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The Influence of Age and Experience 

On Correlations Concerned 

With Mental Tests 



Digitized by the Internet Archive 
in 2011 with funding from 
The Library of Congress 



http://www.archive.org/details/influenceofageexOOjone 



^hxadiaxmi Psucliolagu JiRmwQtxphs 

VOLUME. WHI 

Jfa. 22 



THIS VOLUME. WHICH IS 



IN THE SERIES, WAS EDITED BY 
JAMES ROWLAND ANGELL 



The Influence of Age and Experience 

On Correlations Concerned 

With Mental Tests 



Edward Safford Jones 

Assistant Professor of Psychology, Oberlin College 




Warwick & York. Inc 

Baltimore, Md. 

1917 



UBtl-31 

■T7 



Copyright, 1917, by 
Warwick & York, Inc. 



JAN -4 1918 
©CI.A481959 



CONTENTS 

Page 

1. Introduction 3 

2. Historical 7 

3. Administration of the Tests 25 

4. Results : The Influence of Age and Expe- 
rience on — 

(1) Correlations of Samples of the Same 
Test on Different Years 41 

(2) Relationship of Total Test Average 
and the Different Test Measure- 
ments 51 

(3) Change in Inter -Test Correlations.... 57 

(4) Relationship of School-Grade — com- 
pleted to Test Measurements 67 

(5) Influence of Education on Inter- 
Test Correlations 74 

(6) Meaning of Individual Tests — Sum- 
mary 76 

5. Conclusions 81 

Appendix: List of References, with Table for 
Determining Probable Errors 87 



ACKNOWLEDGMENTS. 

Valuable suggestions as to methods of handling 
the data of this research were received from Messrs. 
Harold D. Rugg and Beardsly Ruml, of the Univer- 
sity of Chicago. In much of the routine connected 
with the computing of correlations, as well as in the 
writing of the text, my wife, Mrs. Frances Jeffery 
Jones, was of inestimable aid. 

To Mrs. H. T. Woolley, with whose permission 
this study was carried on, credit for the collection of 
data is due. Without the steadfast planning and 
the inspirational guidance which came from her, 
no such body of data could have been gathered. 
Amid almost insuperable difficulties she has in- 
sisted on keeping the testing up to a high degree of 
standardization, allowing only skilled and interested 
workers to do the testing, and cheerfully but dog- 
gedly insisting each year on as full a quota as pos- 
sible of "re-tests" of our industrial group. Few 
will realize the obstacles she has faced. 



THE INFLUENCE OF AGE AND EXPE- 
RIENCE ON THE CORRELATIONS 
CONCERNED WITH MENTAL TESTS. 
Section I. 
INTRODUCTORY. 
In this research* we have covered the data of 
four years of testing in the Vocational Bureau of 
Cincinnati. The results of two of these years are 
included in the Woolley and Fischer monograph, 
but we have limited ourselves in a number of ways. 
In the first place, our problem is more specific. We 
are interested in only one phase of the whole experi- 
ment, namely, the correlations between purely men- 
tal measurements, and their variations from year to 
year. In the second place, we have selected the 
records of boys only, and of those boys whose 
records were complete and continuous through the 
four years of testing. Thirdly, we have restricted 
ourselves to those tests which are called "mental," 
paying no attention to such tests as seem to depend 
more on physical ability. Finally, we have paid lit- 



* The present study is a by-product of the work of the 
Cincinnati Vocational Bureau, under the direction of 
Mrs. Helen Thompson Woolley. For an extended re- 
port of the problems and methods of that larger social 
experiment, one is referred to Monograph No. 77 of the 
Psychological Review Monographs, and to "A New Scale 
of Mental and Physical Measurements for Adolescents, 
and Some of Its Uses," in the Journal of Educational 
Psychology for November, 1915. These reports include 
also the age and grade norms in the different mental tests 
as administered by the Cincinnati Vocational Bureau. 



4 INFLUENCE OF AGE AND EXPERIENCE 

tie attention to tests which have not been carried on 
from year to year in much the same form. In 
other words, our emphasis was not on the variety 
of tests and a study of individual tests, but rather 
on the change in the various capacities measured 
by certain tests from year to year as indicated by 
their correlations. 

More specifically, we are interested in answering 
the following questions : 

1. On the basis of our standard psychological 
tests, do persons tend to become more alike from 
year to year? If they do tend to become more 
alike in their mental capacities, the correlations be- 
tween these tests will be smaller from year to year; 
whereas if adolescent boys become separated more 
sharply into the good, mediocre or poor intellec- 
tually, the correlations between the tests will rise. 
(See note on p. 14.) 

2. In the case of each of these standard tests, is 
the first, or a subsequent, testing of an individual 
the more reliable index of the tested capacity? 

3. What tests are best correlated with the 
amount of school training received by the subjects 
of the tests? How does the relationship between 
school-grade-completed and the various tests change 
from year to year under the conditions of the Cin- 
cinnati testing? 

4. What tests are the most reliable measures of 
intelligence over long intervals of time, as con- 



INTRODUCTION J 

trasted with tests giving highly consistent correla- 
tions for short periods? In what sorts of meas- 
urements do the persons tested hold closest to type 
from year to year? 

5. What bearing have these results upon the 
presence of a common intelligence factor? 

We have restricted ourselves entirely to the cor- 
relation method of procedure in getting our con- 
clusions, because it seems to be the most adequate 
means for studying such relationships. It has fre- 
quently been said that the method of correlation 
can prove anything, and we are aware of the pit- 
falls of a wholesale, uncritical use of the method. 
The correlation index between Mental Test A, and 
Function X may be shown to be anywhere from 
to plus .50, depending upon a great variety of fac- 
tors not as a rule considered in the statement. 
Some of these factors are the age of persons tested, 
the sex, the educational status of the group consid- 
ered, the exact method of giving the test (i. e., 
Mental Test A), familiarity with the test through 
practice, and finally, perhaps most important of all, 
the homogeneity of the group. Those who have 
worked to any extent in the field of correlational 
psychology realize the absurdity of such a statement 
as that "the Opposites Test correlates as high as .60 
with English ability, or salesmanship, or what not." 
We shall have to be more explicit as to the condi- 
tions affecting such correlations, adding, for exam- 



6 INFLUENCE OF AGE AND EXPERIENCE 

pie, that the group tested was one of college Fresh- 
men in a Middle Western State Institution who had 
had one previous set of tests a month before, that 
the Opposites list was comprised of hard words 
and given according to the X method, and that Eng- 
lish ability was based on such and such an attain- 
ment. 

We do not anticipate that, in the following pages 
of results, there will be many individual correla- 
tions which will have concrete value to those anx- 
ious to apply the tests for vocational purposes. We 
do believe, however, that the data which we are 
offering are capable of adding to our present infor- 
mation regarding the very complex set of factors 
which make up the average set of correlation in- 
dices. 



Section II. 

HISTORICAL. 

Researches concerned with the correlation 
method of procedure in treating of the results of 
mental tests have been quite fully described in 
many places, and are now so numerous that no at- 
tempt will be made to survey the literature entirely. 
Readers are advised to read such articles as those 
by Whitely ('11)*, Brown ('11), Hart and Spear- 
man ('12),- and Thorndike ('14), to become ac- 
quainted with the origin of "correlational psychol- 
ogy," and also to come in contact with practically 
all the statistical technique now used by psycholog- 
ists in discussing mental tests. Before taking up to 
some extent those special researches which bear 
quite directly on our problems, it might be well to 
summarize briefly the general results which have 
been pretty well agreed upon by all who have 
worked extensively in this field. 

1. Correlations between all sorts of mental meas- 
urements of a desirable nature and with all kinds 
of groups of subjects, tend to turn out positively. 
In the case of most experiments, those tests which 
appear to measure the higher mental capacities, as 
contrasted with tests of abilities on a purely sen- 
sory level, correlate with each other highly. 

2. The degree of correlation between mental 
tests varies markedly according to the group of sub- 
jects tested (even where the same tests have been 



* This refers to a publication in the year 1911. 



8 INFLUENCE OF AGE AND EXPERIENCE 

used and by the same experimenter), showing: 

(a) the dependence of the degree of correlation 
on the heterogeneity of the group, and 

(b) on the tests' meanings to subjects of differ- 
ent age. and educational status. 

3. For the most part, those tests which appear 
to measure closely related abilities have given high 
correlations when tried out together, but numerous 
cases to the contrary have been cited. For exam- 
ple, Thorndike ('14), and Winch ('09), and Wyatt 
('14), have concluded that memorizing abilities are 
highly correlated, more on account of like content 
than because of the mental process. The memor- 
izing of two entirely different materials may show 
no positive correlation. 

4. A fourth result might be added to the out- 
come of mental test researches. There has been 
more and more evidence to indicate, as Spearman 
holds, that a correlation, practically perfect, exists 
between columns of correlation indices of mental 
tests. This has been taken to prove that tests can 
be arranged in the order of their ability to measure 
a hypothetical common factor of intelligence. Some 
writers, however, notably Simpson and Brown, 
have found it difficult to subscribe to such an ar- 
rangement of their tests. 

In searching for an historical background for our 
study, we find the data very meagre. However, 
many important researches have touched on one or 



HISTORICAL y 

another phase of it. In enumerating them, it would 
seem best to classify them under the following- divi- 
sions : 

1. Those bearing on the influence on the corre- 
lations of a difference in the subjects tested. 

2. On the influence of practice on correlations. 

3. On the effect of time intervals on correla- 
tions of samples of the same tested ability. 

(1) Those researches discussing the influence 
of age, intellectual status, or homogeneity of the 
group on the correlations between mental tests. 

Mr. C. Scott ('13) believes that one would find 
in the average normal school that estimates of in- 
telligence and ranking in tests correspond most 
highly at the time of the first year of normal school 
study. He believes this would be true because it 
is the period just before specialization has set in. 
On such an hypothesis, one would expect a higher 
correlation between tests of intelligence among per- 
sons of fourteen years of age, especially when they 
have just come out of the public schools, than among 
the same persons tested after work in the indus- 
tries. Specialization and the levelling influence 
of industrial life might well operate to make many 
persons fair performers in certain mental tasks and 
inefficient in others, thus lowering the correlation 
indices. 

On the other hand, it might be argued that school 
work was the more levelling type of intellectual 



10 INFLUENCE OF AGE AND EXPERIENCE 

performance, and that when once away from its 
routine the brighter persons would go ahead much 
more rapidly than before, and the duller ones, be- 
cause of the lower grade of their jobs, would stay 
practically where they were. 

Burt ('09) seems to have been the first to apply 
the same set of tests to more than one group of sub- 
jects. He gave his set of twelve tests first to a 
group of thirty elementary school boys between the 
ages of eleven and thirteen; he repeated these tests 
on a group of thirteen preparatory school boys of 
about the same age. The distinction between the 
two groups of subjects was not a difference in age, 
but a distinction on the basis of social standing, de- 
termined by the wealth of the parents. As would 
be expected, there was more selection on the part 
of the preparatory school boys, and consequently a 
greater homogeneity of intellectual abilities. This 
was shown by the lower correlations between the 
tests in the study of the preparatory school group. 
Out of 77 compared correlations between tests taken 
by elementary, as well as preparatory, school pupils, 
it was found that 47 of the elementary school corre- 
lations were higher than those of the preparatory 
school, while in one case both were the same. But 
the correlations connected with the preparatory 
subjects are somewhat unstable, because of the 
small number of subjects tested. 

Of more interest than the comparison between 
these two sets of intercorrelations, is the compari- 



HISTORICAL 



11 



son between the correlations obtained by Burt on 
his elementary pupils and the correlations of Calfee 
('13), who worked with four of Burt's tests on a 
group of college freshmen in the University of 
Texas. In every case, the correlations found by 
Calfee, on testing the freshmen, were decidedly 
below Burt's correlations with the same tests. 

Definitely then, the selection which is present in 
the case of college freshmen, where there is marked 
specialization and also elimination of the unfit, 
lowers the correlations. 

The more recent research of Bell ('16), in which 
there was scarcely a correlation index over .30, is 
another instance of the homogeneity of the college 
group. 

Brown ('10) reports a study of a series of mental 
tests tried out on different groups of students, the 
lowest two composed of girls and boys of eleven 
and twelve years of age, and the upper two of uni- 
versity students, men and women. In practically 
every case, the coefficients of variation, or measures 
of the dispersion of the test records, were smaller 
with the older groups of subjects, suggesting the 
greater homogeneity of the older groups. Those 
correlations between tests, which were compared 
from one year to the next, showed also that in the 
older, more selected set of subjects the correlation 
between tests was lower, indicating greater homo- 
geneity. Simpson ('10), working with two groups 
of subjects composed one of college graduates and 



12 INFLUENCE OF AGE AND EXPERIENCE 

the other of derelicts, on combining the two groups, 
found the correlations higher than when they were 
considered separately. 

The study of Bonser ('10) on the reasoning abil- 
ity of children is the first large attempt to study the 
variation in correlatiQiis of mental tests in different 
age and grade groups. He tested 757 children from 
the fourth, fifth, and sixth public school grades. 
The tests were fairly complex, dealing largely with 
the language function, and were classified under 
the four captions of mathematical judgment, con- 
trolled association, selective judgment (including 
the Opposites Test, the only test which compared 
directly with any of ours), and the ability referred 
to as literary interpretation. All but the last type 
of mental tests showed reliable correlations with 
age and school grade. 

One fact of great interest to us in Bonser's study 
is the degree of correlation between the tests and 
the school standing in the different grades. It 
turned out that the higher grades gave better corre- 
lations between school grade and the tests, but he 
affirms that this is due to the greater heterogeneity 
of the higher grades, as there was better distribu- 
tion of mental ability and wider age variation in 
the upper grades than in the lower. This last fac- 
tor explains, perhaps best of all, the divergence of 
these results from the results noted above, namely, 
that lower test intercorrelations occurred in the 
higher school grades. 



HISTORICAL 



13 



Bonser also determined the correlations between 
tests in different age groups, particularly the three 
groups of "lowest 25 per cent, in age," "medium 50 
per cent.", and "highest 25 per cent." He found 
results this time that were comparable to the above- 
cited findings, namely, that the correlations in the 
case of the younger subjects were somewhat higher 
than the corresponding correlations with older sub- 
jects. 

Abelson ('11) worked with a number of tests 
on sub-normal or backward children, and came to 
this conclusion among others, i. e., that it is wrong 
to infer the value of a test in one group of subjects 
on the basis of the correlation connected with it in 
other groups. A test might have a fair degree of 
validity as a measure of intellectual capacity on one 
level of ability or with one age, and yet be mere 
routine, not even challenging real intellectual in- 
sight, on another level of age or mental ability. 
Such a statement, also mentioned by Brown ('11), 
would seem to challenge the validity of many con- 
clusions previously mentioned. Naturally, it might 
be said, the correlations in connection with college 
students would be lower than those in the case of 
boys, because the tests which were hard mental per- 
formances for the boys, thus ranking most reliable 
in sorting out the good from the bad, would be un- 
interesting and intellectually not stimulating for 
college students. 



14 INFLUENCE OF AGE AND EXPERIENCE 

Pyle brings out the same point in his study of 
the mental records of over 200 students, classified 
according to their age from eight to eighteen. The 
tests, which were valuable in differentiating age 
groups among the younger subjects, were not so 
effective in this respect with subjects of more ad- 
vanced age. 

These conclusions as to the influence of age on 
correlation seem to be somewhat uncertain. On 
the whole, it would appear that, when we go up the 
scale in age, especially when considering those 
tested in school, selection and mental homogeneity 
are evidenced by a drop in the correlations between 
mental tests*. 



* Objections might be raised to the argument that low 
correlation tends to be an accompaniment of homogenity 
among subjects. In the ordinary product-moment formula, 

r — — - . homogeneity reduces the size of the devia- 

n <r t o y ' ° J 

tions x and y and, consequently, the numerators of the 
fraction. Now it is argued that homogeneity also insures 
a decrease in the size of the standard deviations, which 
make up the denominator of the fraction. The result 
would be no guaranteed change in the correlation. 

This argument would be convincing if there were a 
straight line regression and only slight deviations from 
the means in each array. But this is never the case with 
mental tests. If one artificially chops off the highest and 
dullest of a large group of persons, it eliminates those 
individuals who have extreme deviations in both functions 
considered. This strikes off with a blow those affecting 
the correlation most positively. This artificial division is, 
however, not likely to interfere with those individuals 
extremely good or poor in one function, and mediocre in 
the other. All such cases operate to keep the S. D's as 



HISTORICAL 



15 



The advantage of our results, in regard to this 
question, is that we dealt with exactly the same sub- 
jects each year, and not with groups of subjects, 
differing as to degree of selection operative among 
them and the amount of school work completed. 
Moreover, the age limits, from fourteen to seven- 
teen years, are not wide enough to raise the objec- 
tion that the tests have radically different meanings 
at one period of testing as compared with another. 

Our data, however, have one serious disadvan- 
tage in attempting to decide the question of the in- 
fluence of age and experience on the intercorrela- 
tions between tests, i. e., the effect of practice is 
involved in all tests beyond the first series given at 
the age of fourteen. The question arises, can we 
estimate the degree of practice and eliminate its 
effect in our work ? This brings us to the next sec- 
tion. 

(2) Those researches discussing the effect of 
former experience and practice on the correlations 
between mental tests. 

The problem does not seem to have been directly 
attacked by many experimenters, but a number of 
researches have taken up the closely related ques- 



high as before, whereas the x y's are negligible; i. e., the 
denominator is not affected as much as the numerator. 

We have tried this artificial selection in the case of the 
Cincinnati subjects. When we disregard a few markedly- 
inferior or superior individuals, whether in scholarship or 
in average mental test standing, the result is a smaller 
correlation between tests. 



16 INFLUENCE OF AGE AND EXPERIENCE 

tion as to whether those who are good in mental 
tests are apt to improve as much, or more, than 
those who are poor. Obviously, if the poor im- 
proved with practice much more than the good, the 
group would tend to even up in ability, and the cor- 
relation between practiced tests would be reduced. 
If, on the contrary, those who are superior in ini- 
tial test performances improve the more on account 
of practice, it would seem that correlation between 
practiced tests (assuming the validity of a general 
intelligence factor) would increase. 

Binet takes the first of these positions, particu- 
larly on the basis of an experiment carried out with 
the five brightest and six dullest of a group of thirty 
pupils. With the cancellation test, tried out at four 
different times, he found that there was greater 
improvement with practice in the case of the dull 
pupils than in the case of the bright. This was 
much more marked in regard to accuracy than to 
speed. He concluded that the differentiation be- 
tween the good and poor, in the case of mental tests, 
diminishes and tends to disappear entirely with con- 
tinued testing of the same function. If this was 
true with all tests, as suggested by Binet, with con- 
tinued practice the correlation between tests would 
approach zero. 

The next research to take up this problem is that 
of Kruger and Spearman ('06), which works over 
the data on continued adding for a period of two 
hours, obtained by Oehrn in 1889. The standing 



HISTORICAL 17 

of each of the subjects for efficiency during the en- 
tire performance was compared with their standings 
during each of the fifteen-minute periods of the 
tests. In harmony with the doctrine of the com- 
mon intelligence factor advanced by Spearman in 
1904, their conclusion was to the effect that prac- 
tice tends to increase the amount of divergence be- 
tween the good and the poor, as evidenced by the 
rise in correlations between total efficiency and spe- 
cial efficiency on account of practice. 

Burt ('09) is the next author to bring up the ques- 
tion of the influence of practice on correlation. He 
found that when from two to four trials of his tests 
were made on elementary grade students, the final 
trials correlated less closely with imputed intelli- 
gence than did the early trials. In all but one of 
the twelve types of measurements, he finds a lower 
correlation between test measurement and imputed 
intelligence on the second trial of the test than on 
the first trial. His conclusion was similar to Binet's 
main conclusion that continued practice with a test 
reduced its correlation with intelligence. If one 
will take note, however, of those correlations which 
concern tests administered three times, it appears 
that, although the third samples of ability correlate 
with intelligence more poorly than the first, yet the 
third samples are somewhat better than the records 
taken the second time. We want to emphasize, 
then, contrary to Burt's statement, that his data 
indicate a drop in the intercorrelations between 



18 INFLUENCE OF AGE AND EXPERIENCE 

tests from the first to the second year and a rise 
from then on. This suggests that perhaps, in at- 
tacking a test for the first time, there is the factor of 
adaptation, common to all tests, which raises inter- 
correlations between tests on the first year higher 
than would otherwise be the case ; and after the 
initial drop in intercorrelations, due to this factor 
common to all tests given for the first time, practice 
does operate to raise the intercorrelations from one 
time to the next. 

Abelson ('11) tested subnormal children and con- 
cluded that, on the average, the intercorrelations 
between tests do not fall, but if anything, rise when 
the same series is repeated. The average intercor- 
relation between tests, given on a number of groups 
(boys and girls), turned out to be .32 for the initial 
trials, .36, .37, .40 in the case of the second, third 
and fourth trials, respectively. 

Whitely ('11) reviews the work of many who 
have studied the effect of practice, and on the basis 
of these and her own results, derived from the 
records of only nine adult subjects, she concludes 
that individuals of low standing can and do im- 
prove more than those of high mental ability. Her 
tests were the discrimination of weights, cancelling 
A's, sorting, and the pencil maze. Her foot-rule 
correlation index, between position at the start and 
gross gain in the case of each of her tests adminis- 
tered twenty different times, was in the neighbor- 
hood of .50. Thorndike objects to these conclu- 



HISTORICAL 19 

tions on the basis of Whitely's other findings, and 
the data of Kirby, Starch, Wells, Thorndike and 
others. In none of these cases are the correlations 
designated in detail, but in every case there is indi- 
cation of a heterogeneity of mental ability greater 
after a session of practice than in the initial trials. 
Thorndike ('14) concludes "the results are rather 
startling. Equalizing practice seems to increase 
differences. The superior man seems to have got 
his present superiority by his own nature rather 
than by superior advantages of the past, since dur- 
ing a period of equal advantage for all he increases 
his lead." 

These conclusions gain slight verification again 
in a recently reported study of Thorndike (Am. 
Jr. Psy. 1916). A recent monograph by Wallin 
('16) gives data from repeating form board tests 
on several hundred children, in which he found that 
the average pupils improved appreciably more than 
the duller or the bright, while the dull improved 
slightly more than did the bright. 

Brown ('13) mentions an experiment by Winch 
concerning the effect of practice on correlation be- 
tween a simple motor test of cancelling all letters, 
and a complex motor test, cancelling a,n,o,s. The 
correlations in the case of boys on the six succes- 
sive days were .29, .44, .59, .48, .50, .47, suggest- 
ing an initial increase from the first to the second 
trial, but from then on no appreciable change. 



20 INFLUENCE OF AGE AND EXPERIENCE 

In contrast to the rather dogmatic conclusions 
advanced by Thorndike to the effect that the bet- 
ter subjects do seem to improve in mental tests 
more than the poor, are the results of the recent re- 
searches by Wells ('15) and Chapman ('15). 
Wells found that those who gained most in adding 
over a period of thirty days did not gain the most 
in the Cancellation Test during the same period of 
practice. There was a high negative correlation 
between improvement in one case and improvement 
in the other case. Chapman worked with six tests 
on 22 college men, repeating each test ten times, and 
found no reliable correlations between improve- 
ments in the different tests, except in the two Can- 
cellation Tests which were quite similar. In his 
correlations between initial standing and improve- 
ment, there were only negative or small positive 
r's, except in the case of the adding and multiply- 
ing tests. 

The last important contribution to the general 
question of the influence of practice on correlation 
is that made by Hollingworth in 1913. He tried 
the same six tests on each of thirteen subjects for 
205 times, and found the correlations between the 
different tests at each of the points along the curve 
of learning. He found a tendency for correlations 
to be markedly higher towards the end of the prac- 
tice curve than initially. He took the correlations 
of each test with each of the others at the following 
stages: (1) at the first trial, (2) the average 



HISTORICAL 



21 



records of the first five trials, (3) the average of 
the twentieth to the twenty-fifth records, (4) the 
average of the 75th to 80th records, (5) the aver- 
age of the 200th to 205th records inclusive. At 
each of these points the average intercorrelation 
of the tests used (Adding, Opposites, Color-naming, 
Discrimination, Co-ordination, and Tapping) was 
.065, .280, .320, .390, and .490 respectively. Un- 
fortunately the comparison between the first and 
the second figures given above is not a valid one, 
as the measurements correlated were not compar- 
able. In the first case, the measurements which 
were correlated were those of single trials (the first 
made), whereas in the following index averages 
five measurements were used for each correlation 
rather than one. Clearly, the correlations between 
such average records would be higher than those 
between single attempts. The rise in the correla- 
tion from the second figure on, is based on compar- 
able data, but it hardly concerns our problem di- 
rectly, as a practice of twenty-five consecutive times 
is not at all similar to two or three previous trials 
of a test. Also, as Hollingworth himself has 
pointed out, tests which have been gone through a 
large number of times would be bound to change 
radically because of constant habituation. (Com- 
pare an attack on the Opposites Test the fifth time 
with a similar attack when the test has been taken 
eighty times by the same subject). 

The results bearing upon our question of the in- 



22 INFLUENCE OF AGE AND EXPERIENCE 

fluence of practice on correlations between mental 
tests seem to be conflicting. On the basis of those 
experiments which deal with subjects similar to 
ours, and with tests comparable in nature, we feel 
justified in concluding that in the intercorrelations 
between mental tests tfcere will be little change due 
to the succeeding practice effects of the Cincinnati 
tests. When tests are given a full year apart, it 
is not likely that any real practice effect will last 
over from one year to the next. In case there is a 
change due to practice, the major evidence seems 
to be in favor of a slight increase in the average 
intercorrelation between tests. 

(3) Those researches discussing the experimen- 
tal evidence dealing with the amount of stability of 
intelligence measures, tried out at two different 
times. 

To make a distinction between a "reliability 
index" and a "stability index," the former refers to 
the correlation between two samples of the same 
test when these are taken soon after each other, and 
the latter refers to correlations between two sam- 
ples separated by long periods of time. 

The experiments on mental tests have frequently 
taken cognizance of the reliability of test measure- 
ments, but few have taken up the question as to how 
faithfully a test measurement will stand for a par- 
ticular capacity over a long period of time. 

Burt, Brown, Abelson, Simpson and others have 
worked with reliability indices between different 



HISTORICAL 23 

samples of the same test. A detailed study of these 
does not concern us, as the reliabilities of various 
tests were widely different, and none of these tests 
given were directly comparable with any in our 
series. Suffice it to say that as a rule those tests 
correlating- most highly with the other mental tests 
or with imputed intelligence had the higher reliabil- 
ity indices. 

Kruger and Spearman ('06) mention that in their 
tests reliability correlations were almost as high 
when the capacities were measured by different peo^ 
pie a week apart as when measured by the same 
person twice in the same day. 

Burt tried a series of tests on boys eighteen 
months after the initial series of tests, during a 
rapid growing period (thirteenth to fifteenth years), 
when interests and amount of knowledge absorbed 
varied greatly, and he found no corresponding vari- 
ations in ability as measured by the tests. The 
capacities measured constituted relatively perma- 
nent endowments. 

Starch ('13), in working on school grades, in the 
case of grammar school children found high con- 
sistency correlations (above .80), especially when 
grades were considered over a number of years in 
the grammar school. Kelley ('15) emphasized the 
long persistence of general and special abilities in 
the case of children in high school. Superiority in 
the grammar grades in a special subject such as 
mathematics was shown by the method of partial 



24 INFLUENCE OF AGE AND EXPERIENCE 

correlations to have a definite counterpart in high 
school mathematics, the factor of general school 
ability remaining constant. 

Wells ('15), working on Adding, Cancelling and 
Tapping Tests for thirty days and then dropping 
them until eight months later, found that in general 
those who gained the most through practice lost the 
most from disuse ; but on the whole subjects held 
to their relative positions faithfully. 

Mrs. Woolley (15), in her article already referred 
to, is the first to give a statement of the amount of 
correlation for the average mental test records on 
two consecutive years, given a year apart. For all 
children tested on the two years, there was a cor- 
relation of .71 with a probable error of .034. The 
physical tests gave a correlation somewhat lower, 
.64. The relationship between physical and mental 
tests on the first two consecutive years is also of 
interest in its bearing upon the effect of age and 
experience on tests in general. The correlation be- 
tween the mental and physical series at fourteen 
was .21, whereas at fifteen years, it was .33. 

In summary, it would appear that the ability of 
individual test measurements to determine a stable 
capacity over a period of time has not been care- 
fully studied anywhere. General gross estimates 
of ability, such as school grades or averages in men- 
tal tests, seem to test capacities which are quite 
stable over long time periods. 



Section III. 
ADMINISTRATION OF THE TESTS. 

To come back to our own problem, it will clearly 
be seen that differences in methods of giving the 
tests, differences in the subjects tested, and in what 
is meant by practice and experience, are so various 
that there is need for us to define more precisely 
the exact nature of our age and experience factors. 
We are interested in the strictly adolescent period, 
between 14 and 18 years of age. It is usually as- 
sumed that the greatest changes in life — both physi- 
cal and mental — appear during this period, so that 
if there be a noticeable change in the mental test 
relationships within short time-intervals, we ought 
to have basis for a generalization regarding it. 

But we are not at all concerned with the factor 
of age isolated from that of general experience in 
the world of affairs. Obviously, to give everyone 
the same experience would be impossible. Hence 
it is necessary to consider the effect of age and ex- 
perience as a combined factor. Furthermore, our 
conception of "experience" must include not only 
the vast sum of sensory-motor reactions peculiar to 
the Cincinnati industrial environment, but also pre- 
vious familiarity with the test in question. To out- 
line the factors concerned in our study, we might 
state that we are interested in knowing the influ- 
ence on the correlations concerned with mental tests 
exerted ( 1 ) , by an advance in years during the 
adolescent period of the average working boy of 



26 INFLUENCE OF AGE AND EXPERIENCE 

Cincinnati; (2), by the series of chance experiences 
undergone by such a group during four years of 
contact with (a), widely different industrial occu- 
pations, and (b), different social conditions and 
miscellaneous educational influences affecting each 
boy to a different degree, and (c), the experience 
of coming to the work-certificate office, and under 
controlled conditions there going through a series 
of mental tests for four consecutive years (each 
year's results with the exception of the first year, 
influenced by one or more previous sets of similar 
tests). 

Notwithstanding the vague and unverifiable char- 
acter of our factor of experience, we feel that in 
the long run some general validity will be found in 
the results. The effect of age and experience on 
typical Cincinnati working boys will not be mark- 
edly different from the influence of the same fac- 
tors elsewhere. 
The Subjects.* 

The subjects whose records are included in this 
study were 203 practically unselected boys, who 
started to work in the industries of Cincinnati at 
the age of fourteen. The work certificate office was 
equipped by Mrs. Woolley in such a way that each 
individual who came into the office to get a work 
permit at the age of fourteen was also given a 
series of mental and physical tests. This was re- 



*The complete records of every subject are on file at the 
Vocational Bureau of Cincinnati. 



ADMINISTRATION OF THE TESTS 27 

gardless of his education (except that no boys who 
had not completed the fifth grade were allowed to 
have certificates), regardless of nationality or race 
(except that no negroes were included), and re- 
gardless of his desire, or the desire of his parents, 
to have the tests given. There were 423 of these 
working boys who were tested in this way, and 
questioned as to their social, educational and indus- 
trial background. As many of them as possible 
were brought back each succeeding year to be re- 
tested and requestioned especially as to their indus- 
trial experiences. Surely the final comparison be- 
tween physical, mental and other factors with their 
industrial and commercial progress will be of great 
value. Up to the time of the main work upon this 
research, the data as to industrial progress of these 
subjects had been gathered only for the first two 
years. The correlation up to the end of these two 
years between mental test proficiency on the one 
hand and the average of wage earnings and perma- 
nency of occupation on the other hand, was .07 and 
.11 respectively (by the Spearman foot-rule for- 
mula, taking 100 cases at random). 

Two conditions were noticeable in bringing about 
this lack of correlation between measured intelli- 
gence and industrial fitness. In the first place many 
influential relatives helped poorly equipped indi- 
viduals into the better paid jobs — jobs not so diffi- 
cult, to be sure, as to demand much intelligence. 



28 INFLUENCE OF AGE AND EXPERIENCE 

There was also a frequent tendency for the better 
class of boys to take up the poorly paid though sub- 
stantial jobs to begin with, in spite of longer periods 
of apprenticeship and lower rate of wages. Both 
of these causes of low correlation will tend to be 
eliminated in time; but for the purpose of this 
thesis no note need be taken of industrial facts of 
whatever kind. It is hard to estimate accurately 
the degree of selection which was present in cut- 
ting down the original number, 423 unselected boys, 
to the 203 whose records are included in this re- 
search. But we feel that practically all this selection 
was of an accidental character, at least of a kind 
not connected with intellectual capacities. There 
were a few, not over 5 per cent., who did refuse 
to come back for one or another of the yearly test- 
series, and our 203 were composed only of those 
who had been tested on each of the four consecu- 
tive years. There was a larger per cent, of cases 
which were not included because of the incomplete- 
ness of test records, due to a number of factors such 
as poor stop-watches, or the insufficiency of experi- 
menters in the office at rush periods ; and only those 
were included who had taken every year at least 
two-thirds of the mental tests with which we were 
interested. Finally, the most important source of 
elimination, including at least 50 per cent, of all the 
rejected cases, was the fact that subjects moved out 
of town or left no trace of their moving to other 
parts of the city. 



ADMINISTRATION OF THE TESTS 29 

Just how much this selection is one connected 
with intellectual standing it is hard to determine. 
We must grant that those who refused at one time 
or another to come back for a re-testing were 
usually below the average ill mental ability (as de- 
termined by previous tests). Also it is true that 
those whose addresses were lost on account of fre- 
quent moving were probably below the mental aver- 
age of the total larger group, but this tendency is 
certainly not significant. An objective measure- 
ment of the amount of similarity between our 203 
cases and the total 423 was made by comparing the 
average test records of the 203 with the original 
total group in the first year. The average for the 
423, obtained by the Woolley method of average 
percentile rating (see page 37), was 54 :70 per cent, ; 
whereas in the case of the 203, the average of the 
first year turned out to be 55.97 per cent., with a 
standard deviation of 15.60 per cent. This shows 
that there is but a slight selection, so far as the in- 
tellectual capacity of our subjects is contrasted with 
the total group. All were fourteen years of age at 
the start, and were tested within two months of each 
subsequent year period for four years. 
The Tests and Methods Used. 

There were a large number of tests used through- 
out the four years of testing, but we decided for 
the purposes of this research to pay attention only 



30 INFLUENCE OF AGE AND EXPERIENCE 

to those which might be designated as "mental," 
as contrasted with the "physical" series of tests. 
Mrs. Woolley ('15) has taken up a discussion on 
the .separation of the tests along this line,, and has 
also given a complete account of all the tests used, 
including scores and norms for each of the various 
tests. (See monograph No. 77, Psy. Rev. Mono., 
and article in Jr. Ed. Psy., Nov., 1915). She has 
laid great stress throughout on the importance of 
keeping strictly to specific directions in giving the 
tests. Those who are interested in administering 
any of the tests mentioned in this research we refer 
to the larger work of Woolley and Fischer (as 
above) for complete instructions. Not only have 
we restricted ourselves to the "mental" series of 
tests as distinct from the physical, but we have paid 
particular attention only to those tests which were 
repeated from one year to another. We have not 
dealt with the results of form-board tests, for ex- 
ample, because they did not correlate well with 
each other from year to year, and because, in many 
cases it seemed to the author that success in them 
depended largely on luck. Moreover, not until the 
third and fourth years did we get form-board tests 
which seemed to compare closely with each other. 
We were interested in no test which did not have 
its counterpart in other years. Otherwise our re- 
sults would not be comparable from one year to 
another. It should be added, however, that in 



ADMINISTRATION OF THE TESTS 31 

every case slight changes have been introduced to 
forestall specific practice effects carrying over from 
one year to the next. (See below). 

The following tests were chosen for specific study 
and measurements from these were used entirely: 
The Cancellation Test, a Substitution Test, Imme- 
diate Rote Memory for Numbers, and Cincinnati 
form of the Sentence Completion Test, and the Op- 
posites Test. Miscellaneous correlations with a 
Cause and Effect Paired Associates Test (given in 
the third year in the place of the Opposites Test), 
and also with a Mutilated Text Completion test in 
the fourth year taking the place of the Sentence 
Completion Test, show that both of these tests were 
measurably different from those for which they 
were substituted.* 

The Cancellation Test was carried out in the sim- 
plest way — crossing a single letter from a mass of 
pied letters of the alphabet (using the Whipple 



* The Mutilated Text accuracy correlated with the Sen- 
tence Ideas of the first year to the extent of only .19, while 
the Mutilated Text speed index (number of ideas per 
second) correlated with sentence index to the extent of .26. 
The Cause and Effect test was more closely related to the 
Opposites test than the above two tests seem to have been. 
Accuracy of Cause and Effect with Accuracy of Opposites 
correlated .27, while speed of Opposites with Cause and 
Effect speed showed a correlation of .37. Because cf thees 
low correlations of consistency it seemed best not to in- 
clude records of the Mutilated Text test or the Cause and 
Effect test in the later reckoning. 



32 INFLUENCE OF AGE AND EXPERIENCE 

small letter form). Two measures were used in 
this test, the accuracy or percentage marked, and 
the speed index, derived by dividing the time by the 
accuracy. The irregularity in the succession of 
scores presented below was due to the fact that dif- 
ferent letters were crossed on different years, "a" 
on the first year, "m" the second year, "w" the 
third, and "a" again on the fourth year. This was 
to avoid the possibility of practice affecting the 
scores of certain individuals. 

The numbers below refer to the arithmetic mean 
and the standard deviation of each of the test meas- 
urements during the four years of the experiment 
on the 203 individuals. The standard deviations 
are in parenthesis in each case. 

1st Year 2nd Year 3rd Year 4th Year 





80.67 


93.88 


90.37 


92.30 




(15.21) 


( 5.56) 


( 7.69) 


( 7.91) 




24.33 


1845 


19.54 


19.93 




( 6.64) 


( 3.55) 


( 4.46) 


( 5.43) 



The particular Substitution Test devised and used 
by Mrs. Woolley is difficult to describe adequately. 
For those who care to use it, the previously men- 
tioned monograph should be referred to in detail. 
The main difference between the Woolley Substitu- 
tion Test and other Substitution tests in frequent 
use is in the last retention page of the Woolley type. 
Not only is the time and accuracy recorded for the 



ADMINISTRATION OF THE TESTS 33 

learning pages (in each of which number-symbol 
substitutions are made with the key before one), 
but also on the final or retention page, in which case 
the key is removed and the subject recalls the indi- 
vidual substitutions from memory. It should be 
added that in no case is the subject able to make 
substitutions in a routine way by referring to previ- 
ously recorded writing of his own, as each line of 
substitutions when completed is covered by the ex- 
perimenter. It turned out that all the measures of 
the Substitution Test correlated positively and quite 
highly together, with the exception of the learning 
speed* and the accuracy of retention. 

1st Year 2nd Year 3rd Year 4th Year 



(Learning Speed)... 1.426 


1.318 


1.2771- 


1.291t 


( .301) 


( -274) 


( .271) 


( .266) 


(Retention Speed)... 1.307 


1.185 


1.284 


1.227 


( .636) 


( .599) 


( .680) 


( -731) 


(Retention Accuracy) 92.21 


93.06 


90.40 


92.79 


(12.10) 


(12.83) 


(13.10) 


(11.60) 



The Memory Test was one in which the subject 
was shown two seven-place numbers, two eight- 
place and two nine-place numbers, and was asked 
to read these different series out loud with the ex- 
perimenter at the rate of one second per digit, re- 
cording them immediately afterwards. At first the 



* The learning speed is obtained by dividing total time 
in seconds by percentage correct. 

f On the third and fourth years, two pages instead of 
three were given as a basis of learning. 



34 INFLUENCE OF AGE AND EXPERIENCE 

scores for the different lengths of digits were kept 
separate, but later, on account of the individual 
fluctuation of separate scores, it was decided to 
pool all the results together, and deal with an aver- 
age "percentage of accuracy of all six series digits. 
We tried other measurements in connection with 
this test. Especially were we interested in finding 
out whether subjects who were variable as to accu- 
racy in one year would also be variable in the next. 
In other words, have we here a reliable index for 
the "capacity for resisting distraction" which is 
measurable in terms of the amount of mean varia- 
tion in the scores of the memory series? Our find- 
ings were negative. In 100 random cases a foot- 
rule R of .11 was all that was evident between the 
mean variation of one year and the next. The span 
of memory, the longest series of digits recalled, was 
also correlated in these 100 cases for the first two 
years, and a much lower reliability index was found 
than in the case of average percentage. So we 
finally considered only the one measurement of rote 
memory, and held to that — the average percentage 
of numbers recalled out of six cards read out loud 
by experimenter and subject together. 

1st Year 2nd Year 3rd Year 4th Year 

Memory Accuracy 76.13 80.47 8483 85.27 

(13.90) (13.80) (10.80) (11.47) 
Our Sentence Completion Test was the type sug- 
gested by Binet originally. A series of beginnings 
of sentences was presented, and the subject was 



ADMINISTRATION OF THE TESTS 35 

asked to complete each sentence. Various methods 
of scoring were arranged for by Mrs. Woolley. 
The types of measurements tried out in correlating 
were (1), the number of grammatically correct sen- 
tences written (referred to later as number O. K.) ; 
(2), the speed of association, measured by the num- 
ber of sentences begun within two seconds' time 
after exposure of their beginnings; (3), the number 
of different ideas written down by the subject in 
the entire blank of thirteen sentences ; (4), the speed 
index, or number of seconds per each idea written. 
The first two measurements were dropped from a 
good deal of the later manipulation of correlations, 
mainly because the usage of different sentence 
blanks of varying degrees of difficulty lowered their 
reliability correlations (between one year and the 
next) too greatly. 

1st Year 2nd Year 3rd Year 4th Year 
Sentences 
(Number O. K.) ... . 11.11 12.10 11.78 

( 1.94) ( 1.28) ( 1.67) 
Assoc. Speed 5.59 6.11 5.33 

( 3.62) ( 3.82) ( 3.62) 
Number of Ideas 18.60 23.29 22.52 

( 5.95) ( 6.78) ( 6.75) 
Speed Index 12.51 11.47 1225 

(5.516) ( 4.88) ( 5.91) 

The Opposites Test was used on all years except 

the third. The first two years we used rather easy 

blanks, whereas in the fourth year we used blanks 

of difficult opposites, made up largely of words 



36 INFLUENCE OF AGE AND EXPERIENCE 

given in Simpson's lists of hard opposites. There 
was some indication of a difference in the mental 
capacity utilized for the easy lists as contrasted with 
the capacity necessary in attacking the more difncu 1 t 
list's of words. It was probably due, however, to 
the emotionally discouraging effect of the hard list 
on many subjects. Several persons who had done 
fair work with the easy list had to be repeatedly 
coaxed before even attempting to go over the list 
of hard words. In every case with the Opposites 
tests, two measurements were considered — the per- 
centage of accuracy and the speed index, or the 
time divided by accuracy. For most purposes it 
was decided that the measure of accuracy better rep- 
resented the test as a whole. The speed index 
showed a smaller reliability from one year to the 
next. 

1st Year 2nd Year 3rd Year 4th Year 
Opposites Accuracy.... 77.45 78.72 51.43 

(16.30) (16.91) (22.74) 

Opposites Index 1.484 1.758 9.836 

( .664) ( .951) (10.89) 

There were two other types of measurements 
which we have used to a large extent, in addition 
to the measurements of the individual tests. The 
first was an average test standing of an individual 
in all the tests on a given year, referred to as 
"yearly average." This was found by averaging 
the numbers standing for the decile divisions into 
which each of the important test measurements of 



ADMINISTRATION OF THE TESTS 37 

an individual fell on a given year. (The system 
of describing a measurement by giving it a number, 
from one to ten inclusive, depending on the standing 
of the individual in comparison to the total number 
of subjects, is explained in full in the Woolley and 
Fischer Monograph.) Also there is a "total-test- 
average," the average of all these yearly totals. 
This final average, covering 57 different test meas- 
urements from four different yearly testings, is to 
our mind a fairly adequate statement of mental in- 
telligence, so far as this can be measured by our 
standard tests. Trying to keep in mind the limits 
of the truth of this comparison, we have used our 
total-test-average quite extensively for the purpose 
of determining the possible change in the relation- 
ship of each specific test measurement to general 
intelligence from year to year. 

A second type of measurement which we used 
quite extensively is that of the school grade which 
the subjects had completed at the time of leaving 
school. It has already been stated that the boys 
tested had completed at least the fifth grade of the 
Cincinnati schools. The percentage of those com- 
pleting the fifth, sixth, seventh and eighth grades 
turned out to be 29, 30, 26, and 15 respectively. 
Although the distribution is not scattered enough 
for the purpose of getting very significant correla- 
tion indices between the amount of schooling: com- 



38 INFLUENCE OF AGE AND EXPERIENCE 

pleted and other functions, yet some interesting- ten- 
dencies are suggested by such statistical treatment. 
The Method of Correlation used almost exclu- 
sively in this research is that of getting the simple 
product-moment correlation index between the dif- 
ferent functions concerned, r = — - — — We are 

n <r x a v 

not interested in the extension of new mathematical 
devices, or in the use of old ones, such as the correc- 
tion formulas of Spearman, which have been ques- 
tioned by Brown and others. It is doubtful whether 
the method of attenuating correlations, on the plea 
that the various yearly records were merely samples 
of exactly the same mental trait, is legitimate. In 
most cases the reliability indices from one year to 
the next are too small. But granting the legitimacy 
of the method, Simpson ('12), Webb ('15) and 
others have questioned the value of the expenditure 
of time involved in raising the average correlation 
index five or ten points. We believe that the raw 
correlation indices furnish us sufficiently accurate 
information upon the relationships with which we 
are interested. It is quite certain that the correla- 
tion ratio index, *\ would have given us higher 

results throughout. As with Brown, all correla- 
tions between a speed and an accuracy measurement 
were slightly "j'd" in their plotting. Notwithstand- 
ing the higher set of indices that would have accrued 
by using the correlation ratio throughout, we feel 
that the extra time involved in this method was not 



ADMINISTRATION OF THE TESTS 39 

compensated for sufficiently. So we have con- 
cerned ourselves with linear regression measure- 
ments only — the product-moment "r" index. 

In the end we have gone somewhat beyond the 
bounds of the simple product-moment formula in 
attempting to present a number of partial correla- 
tions — correlations between mental tests stripped of 
the influence of school-grade-completed. In this 
connection we have utilized the formula for multiple 
correlation introduced by Yule and used in Psy- 
chology by Brown and Kelley. 



Section IV. 
RESULTS. 
Influence of age and experience on correlations be- 
tween the same tests on different years 

After stating the purpose of the research, and de- 
scribing the subjects and tests, it seems only neces- 
sary to add the tables of product-moment correla- 
tions as procured. Tables I and II have to do with 
the influence of age and experience on correlations 
between samples of the same tested capacity on 
different years. Are tests, e. g., of immediate mem- 
ory, much more closely correlated when separated 
by short intervals of time, say one year, than when 
separated by longer intervals of two and three 
years? Between samples of the same test, we 
would hardly expect a closer correlation in the case 
of long-time intervals than in short-time intervals. 

Table I refers to the correlation between the gen- 
eral test averages of the different years, and also 
the correlation of the different year averages with 
the total average. The method of getting these 
averages has been briefly described. It should be 
noted, however, that there is a difference between 
the method used in getting the fourth year averages 
and that used in the case of the other three yearly 
averages. In the fourth year, instead of assigning 
each test record of each individual to a decile divi- 
sion (designated from one to ten) on the basis of 
the records of all the subjects tested that year — be- 
tween 350 and 400 — as was done by Mrs. Woolley, 



42 INFLUENCE OF AGE AND EXPERIENCE 

the individual records were assigned to separate de- 
cile divisions on the basis of only our 203 tested 
persons. This was done because records of all sub- 
jects were not easily accessible to the author in the 
latter- part of this investigation. 

Table I (showing -the relationships between total 
test average and the averages of different years). 

1st Year 2nd Year 3rd Year 4th Year 

Total Average 89 .89 .85 .91 

1st Year Average .74 .69 .76 

2nd Year 74 .71 .76 

3rd Year 69 .71 .73 

4th Year 76 .76 .73 

The probable error of the correlations in the first 
row is approximately .01, and the probable error 
for correlations in the neighborhood of .70 is .024. 
In every case the number of individuals tested was 
203. 

Apparently there is little variation in the amount 
of correlation between the total test average and the 
different averages. It cannot be said whether the 
initial, or one of the later series of tests, conforms 
more closely to actual mental ability. The slight 
deviations in the third and fourth year correlations 
can be explained, largely, no doubt, by the fact that 
certain of the special tests helped to make up the 
averages, but were not included in our report be- 
cause they had no duplicates in other years. 

There is a marked consistency of fidelity to type 
of individuals over long-time periods, as shown by 
the intercorrelations of yearly averages. 



RESULTS 43 

Evidently the fourth year average was slightly 
closer to a reliable mental test statement than the 
other three year averages. This may be due to the 
different method used in computing this year's aver- 
age, as already explained. This is shown by the 
high indices where (1) and (2) are matched with 
(4), as contrasted with the indices of (1) and (2) 
correlated with (3). 

But the significant thing is that the correlations 
of (4) with ( 1 ) stand out as high as, or higher than, 
the correlations of (4) with (2) and with (3). As 
we shall discuss later in full, we feel bound to con- 
clude that the factor of general test ability is so per- 
sistent among the individuals that age and expe- 
rience do not interfere markedly with their relative 
position. 

The next table has to do with the correlations be- 
tween samples of approximately the same test meas- 
urements on different years. In Table II we are 
interested to know first, what reliability have differ- 
ent tests from one year to the next ; i. e., how close 
is the correlation in the case of adjacent years? 
Secondly, what stability do test measurements have 
over longer time intervals? If the correlation be- 
tween years which are not adjacent is markedly less 
than the correlation on adjacent years, we feel jus- 
tified in concluding that this test ability tends to 
change over long-time periods. Whereas, if the 
correlations in the case of longer intervals tend to 



44 



INFLUENCE OF AGE AND EXPERIENCE 



be nearly as great as the correlations between adja- 
cent years, we would conclude that the capacity does 
not change markedly on account of age and expe- 
rience. 

Table II (Correlations between samples of the 
same tested capacities^on different years). 

Samples separated by : 



1-Year Intervals 
(1)(2) (2) (3) (3) (4) 



Cancel. Accur- 
acy 22 .37 

Cancel. Speed 

Index 41 .54 

Subst. Test 

Speed of 

Learn 60 .65 

Retention Page, 

Speed 46 .43 

Retention Page, 

Accuracy 50 .52 

Immed. Mem. 

for Numbers. .61 .62 

Sentence Compl. 

Test — Num- 
ber Correct 

Sentences ... .47 .43 

Assoc'n Speed.. .29 .42 

Number, Diff. 

Ideas 47 .49 

Sentence Speed 

Index 57 .50 

Opposites Test 

Per Cent. Ac- .52 

cur .44 

Speed Index. . . 



.33 

.58 

.81 
.59 
.47 
.63 



2- Year A 3-Year 

Intervals Interval 

(1)(3) (2) (4) (1)(4) 



.19 


.20 


.04 


.43 


.49 


.50 


.50 


.54 


.49 


.41 


.46 


20 


.48 


.47 


.52 


.60 


.55 


.62 


.34 






.39 






.47 






.35 








.49 


.43 




.33 


.43 



RESULTS 



45 



With the exception of the Opposites test indices, 
the probable error varies between .043 for indices 
in the neighborhood of .30 to .030 for indices in the 
neighborhood of .60. The number tested was with- 
in five of 200 in every case. In the case of the 
Opposites Test indices, where 100 or fewer subjects 
were used, the probable errors are somewhat higher, 
varying from .051 for the indices around .30 to .050 
in the case of the index of .52. For a complete table 
of probable errors usable in testing the validity of 
our indices, refer to the appendix. 

The above results show features of great interest, 
both in regard to the specific tests in question, and 
also in regard to the general tendency of different 
types of tests to change from one year to the next. 
It may be of value to consider each test separately 
at first. 

At a glance it can be seen that the speed index 
is more reliable than the accuracy as a test measure- 
ment of the Cancellation Test. It might be argued 
that this is due to the fact that some letters are seen 
with greater ease than others. On this account, ac- 
curacy would be a real factor of intellectual discrim- 
ination in one case, while it would not in others. 
Only carelessness would cause errors in the "m" 
cancellation test, for example. That the letters are 
probably not important factors in the result is 
shown by the fact that there are no high correla- 
tions anywhere, and also that the first and the fourth 



A6 INFLUENCE OF AGE AND EXPERIENCE 

years' results are so strikingly far apart (r = .04), 
in spite of the fact that "a" was cancelled in both 
these years. In the case of the Cancellation speed 
index, however, the correspondence is remarkably 
close for the first and fourth years (r = .50), where 
the letter cancelled was the same for both years. 
The speed index in the Cancellation Test seems to 
be a stable test measurement throughout, changing 
very little from one year to the next. That the 
speed index is so much more constant in this test 
than the factor of accuracy is, we believe, not due 
to the fact that people tend to be assigned more per- 
manently in terms of speed than of accuracy. This 
is disproved by the results of other tests. We con- 
clude, as suggested above, that the phenomenon is 
due to a difference in the attitude towards the test. 
At fourteen years of age, when the Cancellation 
Test is first attacked, the factor of intellectual fore- 
sight is really important and prominent, whereas in 
the later tests, particularly the test given in the 
fourth year, the function tends to become auto- 
matic, and errors are due to a carelessness of an- 
other type. But at neither time is there a close cor- 
respondence between accuracy of Cancellation and 
total intelligence. 

The Substitution Test shows results entirely dif- 
ferent, so far as the factors of speed and accuracy 
are concerned. With the learning pages, and also 
the last retention page, the speed of doing the test 



RESULTS 47 

gives much higher reliability coefficients when adja- 
cent years are considered than is the case when 
longer periods intervene between tests. The accu- 
racy of the retention page, on the contrary, shows 
practically no variation so far as the spread over 
varying lengths of time is concerned. The "r's" 
for longer intervals are as high as those for adja- 
cent years. This may be due to the fact that accu- 
racy of the sort required in such work does not tend 
to shift much among individuals during long periods 
of time. Or, more probably, it is due to the fact 
that the memory aspect of this test is the stabilizing 
influence which counteracts time discrepancies in ac- 
curacy of work, and consequently brings the long 
interval correlations up to such a high point. At 
least we must conclude, in this particular test, that 
although for the adjacent years or short interval 
periods, the correlations are much higher in the case 
of the speed of preliminary learning than with ac- 
curacy of retention, yet, when referring to the sta- 
bility of individuals over longer intervals, accuracy 
correlations are just as high as those of speed. 
There is evidently a greater error in the individual 
measurements of accuracy in retention than in the 
measurement of speed. But the amount of change 
in individuals due to age and experience is not 
nearly so great in the former measurement. 

The Memory Test shows a result very similar to 
that of the accuracy of the Substitution Retention 



48 INFLUENCE OF AGE AND EXPERIENCE 

Page. There is no strikingly close correspondence 
between individuals from one year to the next. The 
correlations of adjacent years is never much over 
.60. But there is a marked faithfulness to type on 
the part of individuals over the whole period of four 
years, greater than in any of the other tests. In 
other words, the important factor in keeping down 
all correlations is apparently the sum of many 
chance disturbing factors, such as inattention, daily 
variation, auditory and ideational distractions, 
which enter into individual test performances to 
hinder the procuring of ideal scores of ability. The 
change in the individual from one year to another 
in this rote memory is not affected strongly by the 
factors of age and experience. 

Because it was not used the fourth year, the Sen- 
tence Completion Test did not give as complete a 
set of correlations as did the preceding tests. In 
this test the first two measurements tried out are 
clearly not as reliable as the measurements of the 
number of ideas written and the speed index. As 
would be expected, age and experience evidently 
have an influence on the factor of the number of 
sentences written correctly, whereas this is not 
clearly true in the case of speed of association (de- 
termined by noting the number of sentences begun 
without pausing longer than two seconds). But 
in both of these measurements, the peculiarities of 
the particular test blanks which were used, and 



RESULTS 49 

other disturbing factors previously mentioned, 
seemed to play too important a part in reducing the 
correlations of reliability. For this reason we have 
not considered these two measurements in most of 
our later correlation tables. 

Regarding the number of different ideas written 
in the Sentence Completion Test and the speed in- 
dex, the results seem to point to the same type of 
conclusions to which we came in the case of the 
Substitution Test measurements. The measure- 
ment concerned with the thinking up of a large 
variety of ideas, apparently a sort of free associa- 
tion and certainly closely connected with a certain 
type of memory, is highly stable over long periods 
compared to the ability to think of these ideas in 
the shortest possible time. 

The Opposites Test does not present results 
clearly in line with the other findings. In this test, 
in the case of long intervals, there is an apparent 
tendency towards a closer fidelity among speed 
measurements than among those of accuracy. We 
find it difficult to account for this in any way. The 
high correlation of the speed index between the first 
and fourth years might, however, be due to the fact 
that the first year and the fourth represented the 
more serious attempts, whereas the second year's 
blank was enough like the first to afford a let-down 
for many who did vigorous, alert work the first 
time. The fourth year's Opposites Test was, on 



50 INFLUENCE OF AGE AND EXPERIENCE 

the other hand, difficult enough to call for the best 
in every one. Again the high stability of the speed 
factor, compared with the accuracy measurement, 
might be explained on the basis of the change in the 
type of test. As was said before, the fourth year 
Opposites Test was a -quite different affair from the 
Opposites Test of the first two years. The distri- 
bution of the subjects was around a far lower per- 
centage value ; and there were a number of persons 
who had been quite accurate during the first year, 
but who fell down badly on account of emotional 
causes when confronted with the harder list. 

SUMMARY. (1) There are two important 
factors to consider regarding the reliability of a 
test-measurement over an interval of time. In the 
first place, we want to know whether the test is a 
reliable one, bringing high correlations between its 
samples, over short intervals of time. In other 
words, is the measurement one which can be closely 
duplicated shortly afterwards? The second factor 
to consider is whether, regardless of the amount of 
reliability of the measurement itself, there is a high 
stability in the tested capacity over long-time inter- 
vals. 

(2) On the basis of the above results, it appears 
that those tests which have memory as an important 
item in their make-up, whether immediate or sec- 
ondary memory, are of the type difficult to measure 
accurately at any one time on account of the disturb- 



RESULTS 5 1 

ing factors which enter into the test procedure. 
But these same tests measure capacities which are 
very stable over long periods of time. Those who 
have good memories, immediate or secondary, ap- 
pear to hold faithfully over a period of three years 
to their relative positions in the group. 

(3)' Those test measurements included in our 
series of tests, which have to do with speed in work, 
appear to be less influenced by the disturbing fac- 
tors in the test administration than are the memory 
measurements, and frequently show a high reliabil- 
ity correlation over short-time periods. But individ- 
uals do not hold as faithfully to type in the case of 
speed measurements over long periods of time. 

(4) In the case of accuracy in mental work, the 
results are not nearly so clear. Apparently with 
routine accuracy (as in the Cancellation Test) there 
is practically no faithfulness to type over long-time 
intervals. With accuracy of a high type, involving 
memory and associational factors, this conclusion 
seems not to be so valid. Our tests are not exten- 
sive enough to warrant definite statements in this 
report. 

The influence of Age and Experience on the Re- 
lationship between the Total-Test-Average and the 
Different Test Measurements. 

We have already referred extensively to the fac- 
tor of Total-test-average, which is the average of 
the test performances covering a period of four 



52 INFLUENCE OF AGE AND EXPERIENCE 

years. This is the closest approach we have to a 
statement of general intelligence, although it is 
obvious that such a total average will be partial in 
its ^inclusion of certain mental capacities and its 
neglect of others. For example, at least three speed 
records of the substitution test were included each 
year, but no measurements referring to accuracy of 
retention in this test. Yet, granting the onesided- 
ness of this total estimate of intelligence, it will 
probably be serviceable to indicate in every case any 
marked change in the way a test is associated with 
intelligence from one year to the next. 

Our question, then, is : Do the tests individually 
or as a whole tend to be correlated more closely to 
the total-test-average at the time of their first trial 
or later? Does previous familiarity with a test, and 
intervening age and experience, tend to make that 
test more, or less, closely related to general-test-in- 
telligence? Table III presents this comparison. 

Table III. (Correlations between Total Test 
Average and Individual Test Measurement.) 

1st Year 2nd Year 3rd Year 4th Year 
Cancellation Accuracy .34 .38 

Cancellation Speed Ind. .49 .31 .43 .42 

Subst Test Retent'n 

Accuracy 22 .22 .28 .30 

Subst. Test Speed of 

Learning 65 .65 .56 .54 

Immediate Mem. Test .70 .63 .56 .68 

Sent. Compl. Number 

of Ideas 36 .34 .24 

Sent. Compl. Speed Ind. .49 .55 .53 

Opposites Accuracy... .18 .35 .51 

Opposites Speed Ind.. .45 .42 .45 



RESULTS 53 

The number tested was approximately 200 in 
every case, with the exception of the Opposites Test 
on the first year, in which case N was slightly less 
than 100. (Refer to appendix for a statement of 
probable errors.) 

There is no general tendency for all tests to be- 
come either more or less closely associated with 
•total-test-intelligence. It depends entirely on the 
individual test, its appropriateness as a real mental 
measurement in different years. 

The Cancellation Test shows an interesting result, 
especially when compared with the results presented 
in Table II. It appears that the measurement of ac- 
curacy is slightly more closely related with general 
intelligence at the end of three years than initially, 
despite the poor stability of the measurement from 
year to year. The speed index, however, in which 
was found a high faithfulness to type among the 
subjects, shows a tendency for a drop in the degree 
of its relationship with total-test-intelligence in each 
succeeding year. In fact, in the fourth series of 
tests, it is almost as valid to use the percentage of 
accuracy as the speed index in picking out the more 
desirable subjects. 

The correlations between the Substitution Learn- 
ing pages and the total-test-intelligence decrease 
from year to year. This suggests the possibility 
for all speed indices to become less and less im- 
portant with repetitions of the tests. The amount 



54 INFLUENCE OF AGE AND EXPERIENCE 

of the drop in this case is so striking that it reveals 
again the general fickleness of this test in measur- 
ing capacity over long interval periods. Evidently 
those who are particularly good at the time of the 
first testing are frequently surpassed at a later time 
by those poorer in general test ability. In the case 
of the retention accuracy, there is an evident rise in 
its relationship to the total-test-average. This may 
be due entirely to the tendency of some subjects, 
while going over the learning pages in the later 
years, to anticipate more definitely the final reten- 
tion page. But on account of the consistency of the 
increase in this correlation, even from the third to 
the fourth year series, we might well be justified in 
concluding that care, such as is called for in our 
Substitution Retention Page, does become more 
important as an index of intelligence from year to 
year. 

In the Memory Test, there is a sameness in the 
correlations from one year to the next, with the 
possible exception of the correlation on the third 
year. This is especially significant considering that 
the scores in this particular rote memory test (see 
page 34) approach more and more to 100 per cent, 
accuracy. If we had a harder memory test, which 
would differentiate more exactly the good from 
the mediocre, we would probably find that our 
memory measurement had become even more close- 
ly related to total-test-intelligence on account of age 



RESULTS 



55 



and experience. As it was, on the fourth year of 
the test as many as 20 got perfect scores, while on 
the first year only four attained 100 per cent. 

The results with the Sentence Completion Test, 
apparently upset any assertion we might feel justi- 
fied in making as to the general yearly decrease in 
the relationship between speed test and total-test- 
intelligence, and a corresponding increase in the 
relationship of accuracy tests to test intelligence. 
The "number of ideas written" might well come 
under the heading of mental accuracy, and yet there 
is a marked fall from the first to the third year in 
the relationship between this measurement and the 
total test accuracy. The nature of the test, however, 
will account for a large amount of this drop. The 
test allows for so much freedom of association, 
since subjects are not told explicitly to write as in- 
volved sentences as possible, that it was evident at 
the time the tests were given that many of the 
brighter boys did not write as many ideas in the 
later years as initially. On the other hand, they 
had been timed directly and urged to hurry up so 
much in the other tests that, although the timing 
of the Sentence-Completion Test was intended to 
be without the subject's knowledge, they did get the 
notion of speed rather than of fullness in what they 
wrote. The fact that the better subjects did speed 
up in their writing, on account of the influence of 
the other time-taking tests, has operated to make 



56 INFLUENCE OF AGE AND EXPERIENCE 

this speed index more important from year to year. 
In fact the third year speed index results are about 
as close as any of the tests to total-test-average. 

The Opposites Test shows a rise in the relation- 
ship between accuracy and total-test-average that is 
very striking. This is-clearly indicative of the quite 
different nature of the fourth year's difficult blanks 
as contrasted with those blanks used on the first 
year. The words used on the fourth year necessi- 
tated a certain amount of understanding to appre- 
ciate their bare meaning, while the first year's easy 
Opposites blanks presented no difficulties to the 
subject so far as grasping the meaning of the 
words was concerned. The hard Opposites list 
measures not only the capacity to write the correct 
Opposites, but the ability to face with self-assur- 
ance a very difficult task. On the whole, then, the 
only conclusion we can make regarding the Op- 
posites test is to the effect that a really difficult 
blank of test-words challenges mental test ability 
much better than the easy blanks. 

SUMMARY. We can say, then, that there is not 
a marked tendency, in the case of most of the 
'measures, towards either a greater or a smaller 
correlation with total-test-intelligence on account of 
age and experience. It is quite certain that no 
general statement can be made that will hold good 
for tests of all kinds. As concluded by Brown, 
Abelson, Desourdes and others, those tests which 



RESULTS 



57 



measure mental ability adequately among subjects 
of one grade of intelligence or age do not fit in well 
as measures of ability in subjects of a different sort. 
At the age of fourteen, and when unsophisticated 
by previous mental tests, speed in work is very 
essential, and accuracy less so ; whereas, in the lat- 
ter years, speed is a less important factor, and the 
ability to be accurate, and especially to face unusual 
and difficult tasks composedly, is of greater signifi- 
cance. Hart and Spearman ('14), on the basis of 
a large number of tests on insane adults, and also 
from their contact with results of tests on normals, 
conclude that accuracy is a more important mental 
trait than speed. We would supplement this by the 
statement that at least accuracy seems to become 
more important than speed, in measuring general 
intelligence as people grow older. 

The Change in the Correlations Between Different 
Tests From One Year to the Next. 
We have presented tables of correlations esti- 
mated to show the change in the validity and mean- 
ing of measures from certain standard mental tests, 
which change was affected by the factors of age and 
experience. This was done in part by showing the 
differences in the reliability of these measurements 
when they were tested out with short and with long 
intervening time periods, and in part by comparing 
the relationship between certain of these measure- 
ments and total-test-intelligence in the first year of 



58 INFLUENCE OF AGE AND EXPERIENCE 

their administration as well as later. Our next 
endeavor will be to find out the change in correla- 
tions between different tests from one year to the 
next. As stated in the introduction, we are espe- 
cially interested in finding out if tests are more or 
less closely correlated with each other at the time of 
their first trial, as compared with later administra- 
tions of the same series. After a survey of the re- 
sults of the preceding sections, it appears doubtful 
whether we can get at any conclusion on this ques- 
tion. Many of the tests have apparently changed in 
their function as mental tests enough to invalidate 
strict comparisons from one year to the next. At 
least it is important that we take into account these 
changes indicated in Tables II and III, in the case 
of each test's correlations. 

Only those tests with a fairly high degree of 
stability were used throughout in these compari- 
sons. Otherwise we would be entirely unable to 
interpret results. To do this we have limited our- 
selves to those tests which gave reliability correla- 
tions of .40 or higher. Three exceptions, however, 
were made to this minimum reliability limit, the 
Substitution retention page speed, and the "number 
of correct sentences" and "speed index" of the Sen- 
tence Completion Test. From our five types of 
tests, repeated on at least three of the years, eight 
measurements were chosen for a comparison of the 
inter-correlations from one year to the next. On 



RESULTS 59 

account of the substitutions already referred to, 
there was an omission of all correlations connected 
with the Opposites Test on the third year, and the 
Sentence Completion Test on the fourth year. A 
complete report of the correlations between tests of 
different kinds is found in Table IV. 

We must admit that our data are quite inade- 
quate to answer our first main question. We can- 
not say whether or not tests as a whole become 
more closely related from one year to the next. 
So many irregularities seem to be present through- 
out the course of the four years, that we are at a 
loss in even attempting to generalize in the case of 
many individual pairs of test correlations. 

In our set of ten groups of four indices each 
(concerning those measurements used throughout 
the four years), there is an unequivocal rise in only 
two of the ten groups — Substitution learning speed 
with Immediate Memory, and the accuracy with 
speed of the retention page of the Substitution Test. 
The later of these two rises may be said to be due 
to a lessening of the factor of accuracy from one 
year to the next. The former is difficult to explain 
without some general intelligence hypothesis (as 
suggested by Hollingworth), and the assumption of 
an increase in correlation due to age and experi- 
ence, including practice. But this explanation 
would have more weight if borne up by results 
from other test measurements. 



X <o 




<D Oi 


*d 


•O C/2 


<D 


£ JDO 




^ E 


xn 


C ol 




nj a) 


<u 


a _t 


Cd 



Table IV. Correlations between different tests 
on each of the four years : 

Substitution £ Sentence 

T3 ^ uS Completion 6 

3 +5 • in 

° *3 . • ~ 

*j *j e g 3 w | 

& ,2 # 2 o 

.27 .23 .16 .25 .16 .07 .12 -.10 

.33 .04 -.02 .22 .25 .02 .15 -.18 

Lane. Jsp. index^ 39 u Q? ^ 26 ^ ^ 

?38 .22 .20 .27 -.06 

.27 .47 .31 .25 .10 .07 .10 .11 

Learning ) .33 .53 .37 .07 .07 .15 .23 .19 

Speed 1 .39 .54 .37 .28 .04 .10 .43 .24 

.38 .45 .31 .43 .24 

.23' .47 .71 .22 .03 .01 .09 .02 

5 Retention | .04 .53 .73 .13 -.01 .04 .03 .13 

S Speed 1 .13 .54 .77 .14 .09 .02 .14 

.22 .45 .82 .19 .03 

.16 .31 .71 .14 .12 .04 -.01 .09 

Retention J -.02 .37 .73 .10 .12 .05 -.10 .16 

Accuracy..) .07 .37 .77 .17 .13 .10 .03' 

.20 .31 .82 .11 .06 

.25 .25 .22 .14 .27 .18 .29 .25 

.22 .07 .13 .10 .24 .05 .26 .18 

.25 .28 .14 .17 .08 .07 .18 

.27 .43 .19 .11 .31 

.16 .10 .03 .12 .27 .61 .45 .09 

, .25 .07 -.01 .12 .24 .50 .48 23 

£ JNo. U. K. ( 26 m w u m s? M 

.24 

f .07 .07 .01 .04 .18 .61 .38 .24 

.02 .15 .04 .05 .05 .50 .36 .13 

.08 .10 .02 .10 .07 .57 .35 

.13 

.12 .10 .09 -.01 .29 .45 .38 .13 

i .15 .23 .03 -.10 .26 .48 .36 .18 

T S P eedIndex i .35 .43 .14 -.03 .18 .44 .35 



Immediate Mem. 



O Ideas 



L 

Opposites Ace. 



.13 



-.10 .11 .02 .09 .25 .09 .24 .13 
-.18 .19 .13 .16 .18 .23 .13 .18 

-.06 .24 .03 .06 .31 .24 .13 



RESULTS 61 

For reference to the probable errors of these indices 
see Appendix. Those correlations concerned with the first 
and second years' Opposites test were made on the basis 
of 100 individuals, or slightly less. All other correlations 
refer to cases in which "n" was approximately 200. 

The remainder of these ten sets of correlations 
give great irregularities from one year to the next, 
or else show no tendency either to increase or de- 
crease on account of age and experience. Evidently 
the variations in the Cancellation Test, different let- 
ters being crossed out on different years, have in- 
terfered with consistency in the correlations con- 
nected with this measurement. It is hard to see 
why Substitution retention accuracy does not become 
more and more like the Immediate Memory meas- 
urement. This seems to support Wyatt's ('14) con- 
clusions as to the distinctness of certain memory 
measurements. Our results are especially important 
since continued experience does not lessen the 
amount of disparity between the memory tests. 
There appear to be few cases of consistent drop in 
the amount of correlation between test-measure- 
ments continued throughout the four years or with 
those tests administered on three of the four years. 
The striking exception to this is the drop in the 
relationship between Immediate Memory and the 
Completion Test speed index from one year to the 
next. It seems odd that this should be the case, 
especially as we have already noted the growing 
close relationship of Completion Test speed with 



62 INFLUENCE OF AGE AND EXPERIENCE 

total-test-intelligence from the first to the third 
year. It is one of the marked discrepancies which 
would have to be faced by those who favor the 
theory of the general intelligence factor and an 
increase in correlation between tests in the case of 
practice. It looks to us as though this particular 
set of correlations, and also some of the less regu- 
lar drops in the amount of correlation between tests 
from one year to the next, strongly intimate an 
actual levelling process in mental ability in the case 
of the Cincinnati subjects. It is certainly not im- 
probable that as people advance in years from four- 
teen to eighteen there is a compensating vocational 
influence present in such a way that those subjects 
who have specialized in the use of one type of 
mental ability are apt to fail in another type. 

In a number of the groups of correlations, we 
note one particular inclination of great interest — 
the fact that many correlations seem to drop from 
the first to the second year, and rise again slowly 
from the second year on. This suggests to us an 
hypothesis which we believe clarifies somewhat the 
marked divergence between the theory of Binet and 
Burt on the one hand, and on the other the belief 
of Spearman and Hollingworth that practice always 
tends to increase the breach of difference between 
people, as shown by rising correlations between 
practiced test measurements. In accordance with 
the suggestion of Binet and of more recent experi- 



RESULTS 63 

mentalists, we believe that original ability to adapt 
to new situations, and to understand the instructions 
such as are given, is enough of a single trait in 
itself to raise the correlation between two per- 
formances beyond what would be the case if the 
instructions were well understood from the be- 
ginning by everyone, and where each subject was 
ready to do his best. Obviously, as the understand- 
ing of instructions does enter into all tests, this 
common permeating influence would help to sep- 
arate individuals into good or bad in all tests alike. 
This would operate to raise the amount of correla- 
tion on the first year to a higher degree than if the 
understanding of the instructions did not enter into 
the situation. In the second year, the instructions 
are presumably well understood, as the tests are no 
longer new to the subject. Then, just because a 
person is quick in understanding instructions does 
not mean that he will be capable in all the tests. 

We would include as the second part of our 
hypothesis the expectation of a steady rise in test 
correlations after the first year. This is partly 
because, as suggested by Hollingworth, the tests 
become more alike due to practice, and partly be- 
cause of the greater predominance of the common 
factor of general intelligence under the conditions 
of practice. If we take the average correlation in 
the case of those tests which were correlated on 
the first three years together, we find that the aver- 



64 INFLUENCE OF AGE AND EXPERIENCE 

age correlation made in connection with each of 
the tests of importance (omitting the Opposites 
test), stands as follows: 

Table V. (The average correlations of each test 
measurement with every other test measurement on 
each of the first three years of testing, Opposites 
Test excepted.) 

1st Year 2nd Year 3rd Year 

Cancell'n Index 18 .14 .21 

Subst. Learning Speed 22 .25 .29 

Subst. Retention Speed 25 .21 28 

Subst. Retention Accuracy 21 .18 .22 

Immed. Memory 23 .15 .21 

Sentence Test: No. O. K 25 .24 .26 

Sentence Test : No. Ideas 19 .17 .20 

Sentence Test: Speed Index... .21 .20 .27 

Average intercorrelations of all 

the tests 217 .193 .242 

By inspection it is clear that the mean variations 

of each of these averages is so great that direct 
comparisons between years in the case of individual 
tests is not very valuable. The uniform change in 
amount of correlation for many of the tests is 
however significant. 

The individual test measurements present some, 
variations of importance. The Sentence Test 
measurements, for example, conform less to the 
average rule of rise in correlations after the first 
year than do the other measurements. This is 
probably due largely to the change in the quality 
of the test itself from one year to the next, as noted 
on page 55. The rise in the correlations, in the case 



RESULTS 65 

of those tests which are of the speed variety, is not 
great except when the speed measurements of the 
first three kinds of tests are correlated with the 
speed index of the Sentence Completion Test. 
Again the change in the type of the test is responsi- 
ble. The practical absence of an alteration in the 
amount of correlations between our two types of 
accuracy-memory tests has already been commented 
upon. It seems, then, as though the rise in correla- 
tions was not due to a greater sameness in those 
tests which appeared to be most alike, but rather 
to an increase in the amount of correlation of those 
tests which are apparently quite different from each 
other. Whatever specialization among Cincinnati 
boys has taken place from one year to the next has 
apparently been a specialization in content, rather 
than in a psychological process. That is, a good 
memory in one type of material does not mean an 
efficient memory of another sort, and speed in one 
test does not correspond to speed in another. So 
far as other types of less closely related measure- 
ments are concerned, such as speed with an accuracy 
measurement, there appears to be steady increase 
from the second to the third and fourth years. 
Whether this is due to the factor of practice entire- 
ly, or to the tendency for boys to separate themselves 
more distinctly under the Cincinnati conditions on 
account of age and experience, we are not ready to 
say definitely. We are inclined to believe the latter. 



66 INFLUENCE OF AGE AND EXPERIENCE 

SUMMARY. (1) It appears that there is no 
marked universal tendency for correlations of test- 
measurements either to increase or to decrease on 
account of age and experience, under the conditions 
of the Cincinnati experiment. There are many 
striking irregularities-which are difficult to explain 
in the course of the correlations from one year to 
the next. 

(2) On the whole, it is evident that many tests 
decrease their correlations from the first to the 
second year, due presumably to the factor of the 
understanding of instructions (common to all tests 
at the time of their first administration). After this 
initial drop in the amount of correlation between 
the tests, there is likely to be a slight increase, on 
the following years, in the amount of correlation. 
Whether this is due to practice alone, or whether 
the factors of age and vocational experience varying 
widely among the subjects contribute to this, it is 
hard to say. We are inclined to believe that the 
vocational life in Cincinnati during these three years 
does aid to some extent in differentiating the good 
from the bad. This is in spite of the fact that, in 
the case of certain types of tests, there is an evident 
evening up process (as in the memory tests), so that 
those who are proficient in one are not correspond- 
ingly proficient in the other, even after practice. 
The increase in the amount of correlation between 
different tests is greater when the tests are appar- 
ently unlike each other than when the tests are alike. 



RESULTS 67 

The Influence of Age and Experience on the Rela- 
tionship Between Different Mental Tests and 
the Amount of School Attendance. 

This topic introduces us to a new measurement 
of ability and the whole question of the influence of 
school training on intellectual capacity. As before 
indicated, our group was made up of subjects taken 
from the fifth, sixth, seventh and eighth grades — 
that is, those who had passed in these grades. 

In this connection the following questions 
arise : Which tests seem to be most closely re- 
lated to the amount of school work procured? 
In the course of the growth of the subjects dur- 
ing the three years away from school, does the 
relationship between school grade and test-in- 
telligence alter markedly? Which tests are re- 
lated the most closely to the amount of schooling 
procured as indicated by the drop in their corre- 
lation with this function on account of age and 
experience? 

As previously mentioned, other researches in 
the field of mental tests (especially Bonser's) 
have attempted to relate the results of mental 
tests with ability expressed in the different school 
subjects, but so far as we know no wholesale at- 
tempts have been made to correlate tests, or the 
average of a number of tests with the total 
amount of school work undertaken by subjects 
of the same age. The following indices are 



68 INFLUENCE OF AGE AND EXPERIENCE 

the correlations between the school grade com- 
pleted and the averages of the mental tests on 
the different years. 

Total 
1st Year 2nd Year 3rd Year 4th Year Ave. 
School Grade.. .51 .45 .51 .66 .63 

The rise in the amount of correlation from the 
third to the fourth year has two sources of ex- 
planation, already noted above : ( 1 ) the differ- 
ence in the tests used — Mutilated Text instead of 
Sentence Completion Text — in the fourth year, 
and (2), a change in the method of computing 
the mental average on the fourth year. The 
irregularity on the second year may be due in 
part to the influence of the puzzle box (Healy 
and Fernald), which was included in the sum- 
marizing of percentile averages in this year, a 
test which correlated well with nothing. Also, 
as suggested above, the understanding of instruc- 
tions was an important item in the first year of 
testing, but less significant in the second year. 
In general it seems safe to conclude that the re- 
lationship of the various tests to school grade is 
not decreased on account of age and experience. 
If anything, there is a slight tendency towards a 
better correlation between the amount of school 
training and the results in the mental tests, even 
after three years of the influence of age and ex- 
perience. 



RESULTS 69 

The correlation reached on the fourth year be- 
tween school-grade-completed and the mental 
average as computed on that year seems, to us, re- 
markable. A good many explanations can be 
forwarded for this possible gravitation of those 
who were low in school ability to a relatively 
lower level of mental ability after leaving school, 
and a similar higher rating of those from the up- 
per school grades. A few individuals who had 
finished the eighth grade, for instance, did get a 
chance to go into the night High School, while 
those who were not at the time through the 
grades, or who could not prepare for the High 
School work by taking one or two years of con- 
tinuation school work, were usually not encour- 
aged to do night school work. So far as further 
school work was concerned, there was an air of 
hopelessness about the boy who had completed 
only the fifth or sixth grade of work. But we 
think this factor was not very influential in the 
long run. Certainly not over five per cent, of 
the present 203 subjects took advantage of 
enough night High School studying to make a 
real difference. 

The stimulus received from the higher school 
grades for more advanced reading and thinking, 
and the better grade of position taken by these 
seventh and eighth grade boys, were probably 
more significant factors in correlating the school- 



70 INFLUENCE OF AGE AND EXPERIENCE 

grade-completed with test intelligence. Possi- 
bly the factor, reviewed and experimentally dem- 
onstrated by Thorndike ('16), of the greater im- 
provability of the more intelligent persons, is of 
some influence. Those coming from the higher 
grades, and consequently of a better intellectual 
calibre, improve more through contact with the 
outside world than do those from the lower 
grades. The table of correlations between the 
school-grade-completed and certain of the men- 
tal tests follow below : 

Table V. (Correlations of school-grade-com- 
pleted with certain of the tests given on the first 
and later years). 

1st Year 2nd Year 3rd Year 4th Year 
Cancellation Accuracy 
Cancellation Speed... 
Substitution Speed... 
Substitution Retention 

Accuracy 02 

Memory (Immed.)... 
Sentence: No. Ideas.. 
Sentence: Speed Index 
Opposites : Accuracy.. 
Opposites : Speed Ind. 

There is little to add to the comments already 
made, except the more definite statement that in 
practically all tests there is as close a relation- 
ship with school-grade-completed in the third 
year after leaving school as immediately after. 
In many tests there is a drop in correlation on 



.23 






.21 


.20 


.05 


.11 


.26 


.21 


.21 


.25 


.28 


.02 


.07 


.04 


.17 


.47 


.49 


.49 


.52 


.15 


.20 


.42 




.44 


.37 


.33 




.10 


.02 




.11 


.33 


.12 




.30 



RESULTS 



71 



the second year, due, no doubt, to the influence 
of adaptation to a new situation in the first year. 

Three facts stand out as particularly important 
to us from a study of the table. In the first place, 
there is a high correlation between the factor of 
memory and the school-grade-completed. Also, 
these factors continue to correlate just as highly 
with age and experience. Apparently the train- 
ing received from school experience in general, 
together with the better types of jobs taken by 
those boys who came out of the higher grades of 
school work, has acted in each successive year to 
maintain the relationship between the school- 
grade-completed and the capacity for rote mem- 
ory as tested. 

A second striking fact, and to us just as signifi- 
cant, is the low correlation between the factor of 
retentive ability and school-grade-completed. 
Either because the school has not trained chil- 
dren in this particular line of efficiency, or be- 
cause intelligence in general does not rely much 
upon this trait in character, the correlation be- 
tween school-grade-completed and retentive ac- 
curacy (as measured in Mrs. Woolley's Substitu- 
tion Test) is practically nil. Only on the last 
year, on account of the influence of age and ex- 
perience, does the relationship between school 
grade and retentive accuracy become at all sig- 
nificant. 



72 INFLUENCE OF AGE AND EXPERIENCE 

The third item of considerable significance to 
us is the low relationship all the way through 
between the accuracy of the Opposites Test and 
the function of school-grade-completed. We 
would be led to expect a fair degree of relation- 
ship between these ^measures, at least as much 
as in the case of memory. The results are clearly 
to the contrary. Neither the ability to write 
down the Opposites to easy words at the age of 
fourteen, nor the ability to write down Opposites 
to hard words at eighteen, is related at all closely 
to the amount of schooling undertaken by chil- 
dren. This corresponds with Bonser's finding, 
that the Opposites Test, although superior to all 
other tests so far as measuring test intelligence 
is concerned, was below two of the tests so far 
as correlation with school grade is concerned. 

As a general maxim, one might be led to con- 
clude somewhat sweepingly that the school was 
giving too much importance to the factor of rapid 
and immediate memory work of a rote character, 
whereas the items of retention and of flexibility 
of ideational control were scarcely credited at 
all. We feel, however, that the problem is too 
complicated to make statements of such a dog- 
matic character, and that various types of inves- 
tigations will be necessary for conviction on this 
point. Whether education, any other than that 
of a fairly specific kind, has any direct effect on 



RESULTS 



73 



such a function as the ability to write opposites, 
has as yet not been proven. The degree of diffi- 
culty of the specific Opposites Test seems to have 
nothing to do with this situation, as the Hard 
Opposites Test correlated much more closely 
with total-test-intelligence than did the Easy Op- 
posites Test, but no better with the school grade 
factor. We have also correlated the accuracy of 
the "cause and effect" Paired Associates Test 
with School-grade-completed, and find a consid- 
erably higher result than in the case of the Oppo- 
sites Tests (r = .38). But this test was clearly 
much more of a memory test, as given by us, 
than a test in controlled association. 

SUMMARY: (1) The amount of school 
work undertaken is fairly well related to intel- 
lectual ability as determined by our mental tests. 
After three years of industrial experience, the re- 
lationship is as close as, if not closer than, it is 
when the children come straight from school. 

(2) The relationship between school grade 
and individual test measurements remains re- 
markably stable for three years after leaving 
school. The amount of correlation in each case 
differs widely according to the type of measure- 
ment. There is a surprisingly high correlation 
between immediate memory and school grade, 
and a corresponding low correlation between our 
educational equipment factor and such measure- 



74 INFLUENCE OF AGE AND EXPERIENCE 

ments as our retentive accuracy in the Substitu- 
tion Test, and Opposites accuracy. Substitution 
learning speed, with its highest reliability corre- 
lations from one year to the next, has only a low 
correlation with school grade completed (r = .25 
on the average). 

The Influence of the Amount of Education on Cor- 
relations With Various Mental Tests. 

We are also interested in noting to what extent 
the amount of school work undertaken is an im- 
portant factor in bringing about positive correla- 
tion between different tests, or samples of the same 
test. The mathematical device used in such a de- 
termination was first emphasized by Yule in his 
work on "The Theory of Statistics," and has been 
used in Psychology by Brown, Wyatt, Kelly and 
others. Following is Yule's notation: 

r ]2 ~ r l3 r 23 



N/(l-n 3 )(l-0 



where rn.s stands for the correlation between the 
functions 1 and 2 with the function 3 constant, or 
ruled out. 



RESULTS 



75 



The following 1 table gives the straight correla- 
tions and the partial correlations (with school grade 
constant) for the first and final records in a num- 
ber of tests : 

School Grade 
Years Straight Constant 

Cancellation Accuracy (1) (4) .04 -.01 

Cancellation Index ( 1 ) (4) .50 .48 

Substitution Speed ( 1 ) (4) .49 .46 

Substitution Retention Ac- 
curacy (1) (4) .52 .53' 

Memory: Immediate Rote. . (1) (4) .62 .50 

Sentence: No of Ideas.... (1) (3) .60 .61 

Sentence: Index (1) (3) .35 .33 

Opposites: Accuracy (1) (4) .43 .42 

It is evident that the only straight correlations 
between tests influenced markedly by the factor of 
school grade are the correlations between samples 
of the Immediate Memory Test. In all other cases 
the relationship between the amount of schooling 
and the individual tests is so low that there is no 
marked change in the degree of relationship be- 
tween tests when the factor of school-grade-com- 
pleted is eliminated. 

We are not interested in presenting complete 
tables of the intercorrelations of tests given on the 
same year with school grade constant, although we 
have computed many of these results. Only those 
correlations connected with immediate memory ap- 
pear to be changed to any significent extent. In 
the first year's test records the correlation of the 
Substitution Test speed with Memory was reduced 



76 INFLUENCE OF AGE AND EXPERIENCE 

from .25 to .18, when school grade was constant, 
and of Memory with Cancellation speed from .25 
to .16. The correlations of Memory with retention 
accuracy, sentence index, and Opposites accuracy 
are, however, not influenced by keeping school 
grade constant. All* other test measurements cor- 
relate so poorly with school grade that their inter- 
correlations are not materially altered by keeping 
the school factor constant. 

Summary Regarding the Characteristics of the 
Individual Tests Measured. 

We have taken up a fairly complete discussion 
of the results of each table of correlations at the 
time of their presentation. Possibly the best 
method of bringing certain results together in final 
form will be to discuss the characteristics of each 
individual test measurement. 

The results from the Cancellation Test agree 
with inferences from Binet's work on practice in 
the case of cancellation, to the effect that accuracy 
is not as reliable a measure as speed. 

But the apparent unreliability of the accuracy 
aspect of the test does not necessarily mean that, in 
picking out good subjects, the test is less valuable 
after experience than initially. The value of the 
test does not alter in its ability to signify intelli- 
gence. If anything, the speed factor tends to be- 
come less associated with total intelligence than ac- 



RESULTS 77 

curacy, with practice and experience, although it is 
a highly stable measurement over intervals of time. 

In general, the results corroborate most of the 
other data on the Cancellation Test (reviewed by 
Whipple in his Manual of Mental and Physical 
Tests). Cancellation of a single letter has not, in 
any extended trial, proved to be highly valuable as 
a diagnostic expedient — particularly the accuracy 
measurement of such Cancellation. 

The Substitution Test has no extended history, 
and the type used by Mrs. Woolley is quite different 
from any of the other varieties in common use. 
For that reason it is hard to make comparisons with 
other works. In cases, however, where a similar 
learning test has been tried there has not been a high 
correlation with imputed intelligence or with the 
records of other tests.* It has not compared for in- 
stance with the Opposites Test, as a valuable men- 
tal measurement to use. Mrs. Woolley found it 
the poorest mental test, Cancellation Test excepted, 
in differentiating the grade groups in the fourteen 
and fifteen year old boys. Its value as a diagnostic 
test for vocational analysis is challenged by the 
author ('17), who tried it out on boys learning teleg- 
raphy. A much lower correlation with estimated 
telegraphing ability was found in the case of the 
Substitution Test than with the Memory or the 
Opposites tests. The results given above indicate 
a poor correspondence of the test with school- 



* See Whipple's Manual, p. 499, f f. 



78 INFLUENCE OF AGE AND EXPERIENCE 

grade-completed, and a considerable degree of in- 
stability, as to the capacity measured, over long in- 
tervals of time. The speed index of the test, how- 
ever, is a highly reliable measure for short-time in- 
tervals. 

The Substitution Test retention accuracy is more 
like the Memory test than the Substitution speed 
index, to the extent that it is a relatively unreliable 
method for giving adequate single measures, but 
seems to test a capacity which is stable over long- 
time periods. 

Our method of testing rote memory has not been 
duplicated by any experimenters who have done 
extensive correlating with mental tests. Sleight 
('11), Wyatt ('14) and Carey ('15) have attempted 
to isolate a common memory factor from the fac- 
tor of general intelligence by the method of partial 
correlations. The first two were unsuccessful, but 
Carey believes there was evidence for a slight spe- 
cial memory factor. Winch showed that, although 
the correlation between two memory tests may be 
low, there may be an association between the tests 
as evidenced by a transfer of practice from one test 
to another. We would hesitate less to say whether 
an immediate memory rote test, such as we have 
used, is able to represent some common memory 
function, if it were not for the fact that an entirely 
different type of memory measurement, represented 
by our Substitution retention accuracy, showed re- 
sults similar to it. 



RESULTS 



79 



Most experimenters who have tried out the relia- 
bility of their test measurements (Brown, Burt, 
Abelson, Simpson and others) have found only a 
mediocre reliability index in the case of memory 
measurements. In the case of stability of the mem- 
ory, we find only one comment, a statement by 
Whitely to the effect that, in a test such as a mem- 
ory test where the function has been frequently ex- 
ercised as compared to capacities less frequently 
exercised, there is little change made on account of 
practice. This seems to fit in well with our find- 
ings. In general, we feel that there is a definable 
memory factor, and that it has the two character- 
istics, (1) that it is difficult to measure reliably on 
account of the chance conditions of the moment, 
and (2) that it is a markedly stable sort of factor 
in the life of each individual over a long period of 
time. Despite the difficulty of measuring the func- 
tion reliably at any one time, it seems to correlate 
very highly with the amount of school work com- 
pleted by the individual. It is interesting to record 
in this connection the comment made by Hart and 
Spearman, similar to a note of Burt's, to the effect 
that, in their opinion, the teacher's estimates of gen- 
eral intelligence were too highly colored by the abil- 
ity of the child in rote memory. 

The Sentence Completion Test was given only 
on the first three years of the testing, so that our 
conclusions are not as complete as in the case of 



80 INFLUENCE OF AGE AND EXPERIENCE 

the other tests already referred to. On the whole, 
the speed of writing per idea seems to be the closest 
measure to our total test intelligence, although the 
mental function represented by it appears to be less 
stable over a period of years than the function rep- 
resented by the number of ideas written. 

We are convinced that the measurements con- 
nected with this test do change in their meaning 
when the test is repeated, possibly because there is 
no intimation of speed given in the instructions. At 
least it is true that the relationship between the dif- 
ferent yearly samples of the same measurements 
and such stationary factors as school-grade-com- 
pleted or total test intelligence, is considerably mod- 
ified. This situation makes us undecided as to the 
relative stability of the various mental capacities 
measured. The fact that the "number of ideas" 
correlates with school standing more closely two 
years after leaving school than immediately after, 
suggests an interesting possibility. The inclination 
to continue writing long sentences when not told to 
do so is a characteristic of those with more school 
training, while the initial writing of long sentences 
is not so, to the same extent. The number of ideas 
written, however, becomes less important in meas- 
uring general intelligence with each repetition. 

Objections have already been raised to the use 
of the two measures designated as "number of sen- 
tences written correctly" and "number of sentences 
written with pauses of less than two seconds." If 



RESULTS 81 

our sentence test blanks were more completely stand- 
ardized, so that we could compensate for the diffi- 
culty of the harder blanks, the results might be dif- 
ferent. However, the speed index, or number of 
ideas per minute, seems to be a highly valuable in- 
telligence determiner, even without standardization. 
The Opposites Test has been widely used by ex- 
perimenters, and to good advantage. Bonser and 
Simpson both refer to it as their best single meas- 
urement of intellectual ability. And those authors 
using it, who have arranged their tests in order of 
a common factor of intelligence, have assigned it to 
a high position on their lists of tests. Our results 
corroborate Bonser's findings in that neither the 
easy nor the hard lists seemed to be closely related 
with school-grade-completed ; whereas the hard list 
at least correlates highly with general intelligence. 
The factor of accuracy seems to be a more reliable 
single measurement than the speed index. It is no 
doubt a matter of attitude towards the test. One 
might be led to emphasize either speed or accuracy 
in the test, and the accuracy factor does not suffer 
as much as speed when relatively disregarded. The 
high correlation of the speed index on the first and 
fourth years is an anomaly hard to explain. Evi- 
dently the attitude of the first attack upon an easy 
list of opposites is more like the attitude towards a 
hard opposites list given for the first time three 
years later, than like the attitude towards a second 
easy list a year later. 



CONCLUSIONS. 

I. There is a marked fidelity to intellectual type 
in individuals throughout the adolescent period of 
growth. A disagreement between the relative 
standings of subjects tested, year after year, is due 
to the- chance factors of individual disposition and 
other incidents of eur present testing methods, 
rather than to any striking change in the relative 
standing of subjects on account of age and varying 
experiences in the world of affairs. This is shown 
by comparing correlations between mental averages 
taken with long-time periods intervening as con- 
trasted with similar correlations administered with 
short-time intervals. 

II. The amount of school work completed also 
correlates well with average mental ability and, if 
anything, the correlation increases on account of 
age and experience in industry. 

III. The reliability index of a test measurement 
(a correlation of samples of the same mental capac- 
ity repeated with short-time intervals) should be 
clearly differentiated from the stability index (a 
correlation of a similar type with long-time inter- 
vals). In general, speed of learning such as the 
measurement used in the Cincinnati Substitution 
Test, is a highly reliable measurement for the test- 
ing of its specific capacity at any particular time. 
But this capacity seems to be relatively unstable 



CONCLUSIONS 83 

over two or three year intervals. Workers who are 
rapid at one time may not be as rapid several years 
later. Our measurements of immediate and reten- 
tive memory are somewhat less reliable for any 
single testing, but they represent capacities which 
are highly stable over long intervals of time. Rou- 
tine accuracy of the kind involved in the Cancella- 
tion Test is a measurement from which nothing can 
be inferred, two or three years after it is recorded. 
Measurements connected with such tests as the Sen- 
tence Completion Test and the Opposites Test are 
apt to change their meanings quite markedly over a 
period of years. This is due either to a change in 
attitude towards the tests or to a variation in the 
difficulty of the blanks used. There is no clear 
evidence that individuals would not be relatively 
true to type in all of these measurements over long 
periods. 

IV. Immediate memory is correlated with the 
amount of school work completed, more highly than 
any of the other tests, and the amount of correla- 
tion does not fall off on account of age and expe- 
rience. As compared with immediate memory, the 
speed tests are not nearly as closely related to the 
grade completed, and they become less associated 
on account of age and experience after the subject 
leaves school. There is a surprising lack of corre- 
lation between ability represented by the Opposites 
Test and the amount of school work undertaken. 
The difficulty of the blanks seems to make no dif- 
ference in this respect. 



84 INFLUENCE OF AGE AND EXPERIENCE 

V. On the basis of results procured for partial 
correlation with the usual formula, the amount of 
school work undertaken was not influential in bring- 
ing about any inter-correlations of test measure- 
ments. Some of the measurements connected with 
immediate memory are exceptions. 

VI. We feel hesitant in drawing a conclusion 
regarding the tendency for people of adolescent age 
to become more or less alike as they grow older. A 
review of previous researches, and also a notation 
of the way our tests have changed in their meaning 
on account of age and experience, have convinced 
us that we cannot be too dogmatic in this respect. 
The change in the amount of correlation between 
similar tests from year to year is probably due to 
varying degrees of familiarity with the test, rather 
than to an age factor. The second year's inter-test 
correlations are slightly lower than those correla- 
tions of the first year, because, we believe, the un- 
derstanding of instructions of the tests is not so im- 
portant on the second year. This later factor is 
common to all tests and especially important at 
their initial presentation. It tends to raise correla- 
tions above what would otherwise be the case. 
After the first year there seems to be a rise in the 
amount of correlation between tests. We believe 
that the varying conditions of work in Cincinnati 
after the age of sixteen, and perhaps other factors, 
have operated to make the good slightly better, and 
the poor relatively poorer than they were at the age 
of fourteen. 



CONCLUSIONS 85 

VII. The practical issues drawn from these con- 
clusions are, we believe, of great importance for 
future vocational testing-. In the first place, we be- 
lieve we have verified an opinion held by many that 
one well-rounded testing of an individual is likely 
to place his general intellectual rank for several 
years to come. 

Secondly, we believe we have shown clearly that 
tested capacities in an individual may vary markedly 
in their stability, and that memorizing ability — if 
one can generalize to this extent — is a more stable 
function than speed or accuracy in routine work. 
It appears that a thorough testing out of memory 
will give a more permanent index of ability than 
other forms of testing. 

School systems will, it seems probable, adopt 
some form of Mental Testing of their children. In 
order to determine what types of test are desirable 
and how often there should be administered, inves- 
tigations along the lines indicated above will be in- 
creasingly imperative. 



APPENDIX. 

References Cited in This Research. 

AbElson (1911), Br. Jr. Psy. 4, 159, "The measure- 
ment of Mental Ability of Backward Children." 

Bell, J. C. (1916), Jr. Ed. Psy. 7, 281-99, "Mental 
Tests and College Freshmen." 

Binet, A. (1899), Annee Psychol. 6, 248, "Atten- 
tion et Adaptation." 

Bonser, F. G. (1910), T. C. Contributions to Ed. 
37. "The Reasoning Ability of Children." 

Brown, Wm. (1913), Br. Jr. Psy. 6, 223, "The 
Effects of 'Observational Errors' and Other 
Factors Upon Correlations in Psychology." 

Brown, Wm (1911), "Mental Measurement." 

Burt, Cyril (1909), Br. Jr. Psy. 3, 94-177, "Exper- 
imental Tests of General Intelligence." 

Calfee, M. (1913), Jr. Ed. Psy. 4, 223-31, "College 
Freshmen and Four Intelligence Tests." 

Chapman, J. C. (1915), Col. U. Contribs. to Ed. 63, 
"Individual Differences in Ability and Im- 
provement, and Their Correlations." 

Carey, N. (1915), Br. Jr. Psy. 8, 70-92, "Factors in 
the Mental Processes of School Children." 

Hart, H. and Spearman, C. (1912), Br. Jr. 5, 56- 
84, "General Ability, Its Existence and Na- 
ture." 

Hart, H. and Spearman C. (1914), Jr. Abn. Psy. 
9, 217-64, "Mental Tests in Dementia." 

Hollingworth, H. L. (1913), Jr. Ed. Psy. 4, 405- 
14, "Correlations of Abilities as Affected by 
Practice." 



APPENDIX 87 

Hollingworth, H. L. (1914), Psy. Rev. 21, 1-8, 
"Individual Differences Before, During and 
After Practice." 

Jones, E. S. (1917), Jr. Ed. Psy. 8, 27-34, "The 
Woolley Tests Applied to the Detection of 
Ability in Telegraphy." 

KEllEy, T. L. (1915), T. C. Contribs. to Ed. 71, 
"Educational Guidance." 

Kruger, F. and Spearman, C. (1907), Zeitsch, f. 
Psy. 44, 50ff\, "Die Korrelation Zwischen Ver- 
schiedenen Geistigen Leistungsfahigkeiten." 

Pyle, W. H. (1913), Jr. Ed. Psy. 4, 61-70, "Stand- 
ards of Mental Efficiency." 

Simpson, B. R. (1912), T. C. Contribs. to Ed., 
"Correlations of Mental Abilities." 

SeEight (1911), Br. Jr. Psy. 4, 389, "Memory and 
Formal Training." 

Scott, C. A. (1913), Jr. Ed. Psy. 4, 509-24, "Gen- 
eral Intelligence or School Brightness." 

Starch, D. (1913), Jr. Ed. Psy. 4, 415-18, "Corre- 
lations Among Abilities in School Subjects." 

Stern, Wm. (1914), "Psychological Methods of 
Testing Intelligence." 

Thorndike, E. (1914), Educational Psychology 
Vol. 3. 

Thorndike, E. (1915), Am. Jr. Psy. 27, 550 
"Notes on Practice, Improvability, Etc." 

Walxin (1916), Psy. Rev. M. S. 94, "Psycho-mo- 
tor Norms for Diagnosis." 

Webb, E. (1915), Br. Jr. Psy. Mon. Sup. 3, "Char- 
acter and Intelligence." 



CO INFLUENCE OF AGE AND EXPERIENCE 

Wells, F. L. (1915), Am. Jr. Psy. 26, 58-67, "Note 
On the Retention of Acquired Characteristics." 

Whipple, G. M. (1914-15), "Manual of Mental 
and Physical Tests." 

Whitely, M. T. (1911), Archives of Psy. 19, "A 
Study of Individual Differences." 

Winch, W. H. 1909), Br. Jr. Psy. 3, 386-405, "The 
Transfer of Improvement in Memory in School 
Children." 

WoollEy, H. T. and Fischer, C (1914), Psy. Rev. 
M. S. 77, "Mental and Physical Measurements 
of Working Children." 

WoollEy, H. T. (1915), Jr. Ed. Psy. 6, Nov., "A 
New Scale of Mental and Physical Measure- 
ments." 

Wyatt, S. (1914), Jr. Exp. Ped. 2, 292-7, "The In- 
ter-Relations of Memory Performance." 

Yule, U. (1912), "An Introduction to the Theory 
of Statistics." 

A table to infer the probable error of Correlation 
for different values of indices, by the formula 

1 — r' 

P. E. = .6745 

n 
(a) Where n = approximately 200 — the case 
with all measurements in the Cincinnati series of 
tests, with the exception of the opposites test meas- 
urements on the first and second year. 



APPENDIX 89 

(b) Where n = approximately 100 — the case 
with these measurements concerned with the oppo- 
sites test on the first and second years. 



Value of 


P.E. 


P.E. 


Value of 


P.E. 


P.E. 


r 


n=200 


n=100 


r 


n— 200 


n=100 


.00 


.048 


.067 


.60 


.030 


.043 


.10 


.047 


.066 


.70 


.024 


.034 


.20 


.046 


.065 


.80 


.017 


.024 


.30 


.043 


.061 


.90 


.009 


.013 


.40 


.040 


.057 


1.00 


.000 


.000 


.50 


.036 


.051 









